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Cisco Security Advisory

Cisco IOS Software Crafted TCP Packet Denial of Service Vulnerability

Advisory ID: cisco-sa-20100324-tcp

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100324-tcp

Revision 1.1

Last Updated  2012 September 21 19:12  UTC (GMT)

For Public Release 2010 March 24 16:00  UTC (GMT)


Summary

Cisco IOS® Software is affected by a denial of service vulnerability that may allow a remote unauthenticated attacker to cause an affected device to reload or hang. The vulnerability may be triggered by a TCP segment containing crafted TCP options that is received during the TCP session establishment phase. In addition to specific, crafted TCP options, the device must have a special configuration to be affected by this vulnerability.

Cisco has released free software updates that address this vulnerability.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100324-tcp.

Note: The March 24, 2010, Cisco IOS Software Security Advisory bundled publication includes seven Security Advisories. All the advisories address vulnerabilities in Cisco IOS Software. Each advisory lists the releases that correct the vulnerability or vulnerabilities detailed in the advisory. The table at the following URL lists releases that correct all Cisco IOS Software vulnerabilities that have been published on March 24, 2010, or earlier:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100324-bundle

Individual publication links are in "Cisco Event Response: Semiannual Cisco IOS Software Security Advisory Bundled Publication" at the following link:

http://www.cisco.com/web/about/security/intelligence/Cisco_ERP_mar10.html

Affected Products

Vulnerable Products

Vulnerable devices are running an affected version of Cisco IOS Software, and are configured for any of the following:

  • A specific TCP window size
  • TCP path MTU discovery (PMTUD)
  • Stateful Network Address Translation (SNAT) with TCP as the transport protocol

Configurations Using a Specific TCP Window Size

Devices configured to use a specific TCP receive window size for connections originating on the device are affected by this vulnerability. A device configured with a specific TCP receive window size has the following command in its configuration:

ip tcp window-size <window size, from 0 to 1073741823>

If the TCP window size has not been explicitly configured with the command ip tcp window-size <window size, from 0 to 1073741823> then the device is not affected by the vulnerability.

Configurations Using Path MTU Discovery

Devices configured to use PMTUD for TCP connections originating or terminating on the device are also affected by this vulnerability. Different Cisco IOS Software features may allow to enable or disable PMTUD on a per-feature basis. The following list contains features known to enable PMTUD for TCP connections:

  • TCP over IPv4: the ip tcp path-mtu-discovery command enables PMTUD for all new TCP over IPv4 connections from the device. This command is disabled by default.
  • TCP over IPv6: PMTUD is enabled by default for IPV6 and cannot be disabled.
  • Border Gateway Protocol (BGP): recent versions of Cisco IOS Software (Cisco IOS Release 12.2(33)SRA, 12.2(31)SB, 12.2(33)SXH, 12.4(20)T and later releases) automatically enable PMTUD for all BGP neighbor sessions when BGP is configured. Refer to http://www.cisco.com/en/US/docs/ios/12_2sr/12_2sra/feature/guide/srbgpmtu.html for details.

Other features like generic routing encapsulation (GRE), IP-in-IP tunneling, and Layer 2 Tunneling Protocol (L2TP) also allow the use of PMTUD. However, these are not related to TCP services and therefore are not affected by this vulnerability.

Configurations Using Stateful NAT with TCP as the Transport Protocol

Devices configured to use SNAT are also affected by this vulnerability. A device configured to use SNAT with TCP as the transport protocol has the following commands in its configuration:

ip nat Stateful id <stateful NAT ID number>
     redundancy <redundancy group name>
         ...
         protocol   tcp
!

Note that to be affected under an SNAT configuration scenario, the SNAT transport protocol must be TCP. Recent versions of Cisco IOS Software do not support the use of TCP as the SNAT transport protocol (they only support UDP), in which case the use of SNAT does not make a device vulnerable. SNAT is not enabled by default, and when SNAT is configured, the default transport protocol is TCP if the Cisco IOS Software release supports TCP as a transport protocol for SNAT.

Determining The Cisco IOS Software Version

To determine the Cisco IOS Software release that is running on a Cisco product, administrators can log in to the device and issue the show version command to display the system banner. The system banner confirms that the device is running Cisco IOS Software by displaying text similar to "Cisco Internetwork Operating System Software" or "Cisco IOS Software." The image name is displayed in parentheses, followed by "Version" and the Cisco IOS Software release name. Other Cisco devices do not have the show version command or may provide different output.

The following example identifies a Cisco product that is running Cisco IOS Software Release 12.3(26) with an installed image name of C2500-IS-L:

Router#show version
Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-IS-L), Version 12.3(26), RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by cisco Systems, Inc.
Compiled Mon 17-Mar-08 14:39 by dchih

<output truncated>

The following example identifies a Cisco product that is running Cisco IOS Software Release 12.4(20)T with an installed image name of C1841-ADVENTERPRISEK9-M:

Router#show version
Cisco IOS Software, 1841 Software (C1841-ADVENTERPRISEK9-M), Version 12.4(20)T, RELEASE SOFTWARE (fc3)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Thu 10-Jul-08 20:25 by prod_rel_team

<output truncated>

Additional information about Cisco IOS Software release naming conventions is available in "White Paper: Cisco IOS Reference Guide" at the following link: http://www.cisco.com/warp/public/620/1.html.

Products Confirmed Not Vulnerable

Cisco IOS XR Software is not affected.

Cisco IOS XE Software is not affected.

No other Cisco products are currently known to be affected by this vulnerability.

Details

Cisco IOS Software is affected by a denial of service vulnerability that may allow a remote unauthenticated attacker to cause a device reload or hang.

The vulnerability may only be triggered by a TCP segment received during the TCP session establishment phase. The received TCP segment must contain crafted, not malformed, TCP options. A TCP three-way handshake does not need to be completed to exploit the vulnerability.

To be affected by this vulnerability, a device must be configured for any of the following:

  • A specific TCP receive window size
  • PMTUD
  • SNAT with TCP as the transport protocol

Refer to the Affected Products section for additional details on these configurations.

The vulnerability exists in the TCP options processing code of Cisco IOS Software. When the vulnerability is triggered, Cisco IOS Software enters an infinite loop that may cause the device to reload or hang. The following syslog messages may indicate that this vulnerability has been exploited:

%SYS-3-CPUHOG: Task is running for (128004)msecs, more than (2000)msecs (23/1),process = IP Input.
-Traceback= 0x41CA6AC4 0x41C83170 0x41A22704 0x41F249D4 0x41A24A34 0x41B24C58 
%SYS-2-WATCHDOG: Process aborted on watchdog timeout, process = IP Input.

This vulnerability is addressed by Cisco bug ID CSCsz75186 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2010-0577.

BGP Considerations

This vulnerability could be exploited through the BGP port (TCP port 179) if all the following conditions are met:

  • The device is configured for one or more of the features that make a device affected, as explained above. Note that in recent versions of Cisco IOS Software, configuring BGP automatically enables PMTUD for all BGP neighbor sessions.
  • The source IP address of an attack packet is the IP address of a configured BGP peer.
  • If the BGP TTL Security Hack (BTSH)/Generalized TTL Security Mechanism (GTSM) is configured, the TTL of the received attack packet is within the allowed TTL range.
  • If the BGP peering session is protected by the TCP MD5 option, the attack packet has the correct MD5 hash.

Vulnerability Scoring Details

Cisco has provided scores for the vulnerability in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this Security Advisory is done in accordance with CVSS version 2.0.

CVSS is a standards-based scoring method that conveys vulnerability severity and helps determine urgency and priority of response.

Cisco has provided a base and temporal score. Customers can then compute environmental scores to assist in determining the impact of the vulnerability in individual networks.

Cisco has provided an FAQ to answer additional questions regarding CVSS at

http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html.

Cisco has also provided a CVSS calculator to help compute the environmental impact for individual networks at

http://intellishield.cisco.com/security/alertmanager/cvss.

CSCsz75186 -- TCP crash by watchdog timeout due to crafted TCP segment

Calculate the environmental score of CSCsz75186

CVSS Base Score - 7.1

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Medium

None

None

None

Complete

CVSS Temporal Score - 5.9

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

Impact

Successful exploitation of the vulnerability may cause the affected device to reload or hang. Repeated exploitation could result in a sustained denial of service condition. In the case of a hang, cycling power to the device may be required to put the device back in service.

Software Versions and Fixes

When considering software upgrades, also consult http://www.cisco.com/go/psirt and any subsequent advisories to determine exposure and a complete upgrade solution.

In all cases, customers should exercise caution to be certain the devices to be upgraded contain sufficient memory and that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, contact the Cisco Technical Assistance Center (TAC) or your contracted maintenance provider for assistance.

Each row of the Cisco IOS software table (below) names a Cisco IOS release train. If a given release train is vulnerable, then the earliest possible releases that contain the fix (along with the anticipated date of availability for each, if applicable) are listed in the "First Fixed Release for this Advisory" column of the table. The "First Fixed Release for all Advisories in 24 March 2010 Bundle Publication" column indicates the earliest possible releases which have fixes for all the published vulnerabilities in this Cisco IOS Security Advisory bundled publication. Cisco recommends upgrading to the latest available release where possible.

Major Release

     Availability of Repaired Releases

Affected 12.0-Based Releases

First Fixed Release for this Advisory

First Fixed Release for all Advisories in 24 March 2010 Bundle Publication

There are no affected 12.0 based releases

Affected 12.1-Based Releases

First Fixed Release for this Advisory

First Fixed Release for all Advisories in 24 March 2010 Bundle Publication

There are no affected 12.1 based releases

Affected 12.2-Based Releases

First Fixed Release for this Advisory

First Fixed Release for all Advisories in 24 March 2010 Bundle Publication

12.2

Not Vulnerable

Not Vulnerable

12.2B

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release. Releases up to and including 12.2(4)B8 are not vulnerable.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2BC

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release. Releases up to and including 12.2(4)BC1b are not vulnerable.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2BW

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2BX

Vulnerable; first fixed in 12.4

Releases up to and including 12.2(2)BX1 are not vulnerable.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2BY

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.Releases up to and including 12.2(2)BY3 are not vulnerable.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2BZ

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2CX

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2CY

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2CZ

Vulnerable; migrate to any release in 12.2S

Vulnerable; migrate to any release in 12.2SRE

12.2DA

Not Vulnerable

Not Vulnerable

12.2DD

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2DX

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2EW

Not Vulnerable

Not Vulnerable

12.2EWA

Not Vulnerable

Not Vulnerable

12.2EX

Not Vulnerable

Releases up to and including 12.2(37)EX are not vulnerable.

Releases 12.2(44)EX and later are not vulnerable; first fixed in 12.2SE

12.2EY

Not Vulnerable

Releases prior to 12.2(37)EY are vulnerable, release 12.2(37)EY and later are not vulnerable

12.2EZ

Not Vulnerable

Not Vulnerable

12.2FX

Not Vulnerable

Not Vulnerable

12.2FY

Not Vulnerable

Not Vulnerable

12.2FZ

Not Vulnerable

Not Vulnerable

12.2IRA

Not Vulnerable

Vulnerable; first fixed in 12.2SRC

12.2IRB

Not Vulnerable

Vulnerable; first fixed in 12.2SRC

12.2IRC

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2IRD

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2IXA

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2IXB

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2IXC

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2IXD

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2IXE

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2IXF

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2IXG

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2IXH

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2JA

Releases up to and including 12.2(4)JA1 are not vulnerable.

Releases up to and including 12.2(4)JA1 are not vulnerable.

12.2JK

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2MB

Not Vulnerable

Not Vulnerable

12.2MC

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; first fixed in 12.4

12.2MRA

Not Vulnerable

Not Vulnerable

12.2S

Not Vulnerable

Releases prior to 12.2(30)S are vulnerable, release 12.2(30)S and later are not vulnerable;

12.2SB

Not Vulnerable

12.2(33)SB8

12.2(31)SB18; Available on 24-MAR-10

12.2SBC

Not Vulnerable

Vulnerable; migrate to any release in 12.2SRE

12.2SCA

Not Vulnerable

Vulnerable; first fixed in 12.2SCB

12.2SCB

Not Vulnerable

12.2(33)SCB6

12.2SCC

Not Vulnerable

12.2(33)SCC1

12.2SCD

Not Vulnerable

Not Vulnerable

12.2SE

Not Vulnerable

12.2(50)SE4; Available on 25-MAR-10

12.2SEA

Not Vulnerable

Not Vulnerable

12.2SEB

Not Vulnerable

Not Vulnerable

12.2SEC

Not Vulnerable

Not Vulnerable

12.2SED

Not Vulnerable

Vulnerable; first fixed in 12.2SE

12.2SEE

Not Vulnerable

Vulnerable; first fixed in 12.2SE

12.2SEF

Not Vulnerable

Not Vulnerable

12.2SEG

Not Vulnerable

Releases prior to 12.2(25)SEG4 are vulnerable, release 12.2(25)SEG4 and later are not vulnerable; first fixed in 12.2SE

12.2SG

Not Vulnerable

Releases up to 12.2(31)SG1 are not vulnerable; releases 12.2(40)SG and later are not vulnerable.

12.2SGA

Not Vulnerable

Not Vulnerable

12.2SL

Not Vulnerable

Not Vulnerable

12.2SM

Not Vulnerable

Not Vulnerable

12.2SO

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2SQ

Not Vulnerable

Not Vulnerable

12.2SRA

Not Vulnerable

Vulnerable; first fixed in 12.2SRD

12.2SRB

Not Vulnerable

Vulnerable; first fixed in 12.2SRD

12.2SRC

Not Vulnerable

12.2(33)SRC5

12.2SRD

Not Vulnerable

12.2(33)SRD3

12.2SRE

Not Vulnerable

Not Vulnerable

12.2STE

Not Vulnerable

Not Vulnerable

12.2SU

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2SV

Not Vulnerable

Releases up to and including 12.2(18)SV2 are not vulnerable.

12.2SVA

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2SVC

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2SVD

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2SVE

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2SW

Not Vulnerable

Releases up to and including 12.2(25)SW3 are not vulnerable.

Releases 12.2(25)SW12 and later are not vulnerable; first fixed in 15.0M

12.2SX

Not Vulnerable

Vulnerable; first fixed in 12.2SXF

12.2SXA

Not Vulnerable

Vulnerable; first fixed in 12.2SXF

12.2SXB

Not Vulnerable

Vulnerable; first fixed in 12.2SXF

12.2SXD

Not Vulnerable

Vulnerable; first fixed in 12.2SXF

12.2SXE

Not Vulnerable

Vulnerable; first fixed in 12.2SXF

12.2SXF

Not Vulnerable

12.2(18)SXF17a

12.2SXH

Not Vulnerable

12.2(33)SXH6

12.2SXI

Not Vulnerable

12.2(33)SXI2a

12.2(33)SXI3

12.2SY

Not Vulnerable

Vulnerable; migrate to any release in 12.2SRE

12.2SZ

Not Vulnerable

Vulnerable; migrate to any release in 12.2SRE

12.2T

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.Releases up to and including 12.2(4)T7 are not vulnerable.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2TPC

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2XA

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XB

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XC

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XD

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XE

Not Vulnerable

Not Vulnerable

12.2XF

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XG

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XH

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XI

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XJ

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XK

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XL

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XM

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XN

Not Vulnerable

Releases prior to 12.2(33)XN1 are vulnerable, release 12.2(33)XN1 and later are not vulnerable; first fixed in 12.2SRC

12.2XNA

Please see Cisco IOS-XE Software Availability

Please see Cisco IOS-XE Software Availability

12.2XNB

Please see Cisco IOS-XE Software Availability

Please see Cisco IOS-XE Software Availability

12.2XNC

Please see Cisco IOS-XE Software Availability

Please see Cisco IOS-XE Software Availability

12.2XND

Please see Cisco IOS-XE Software Availability

Please see Cisco IOS-XE Software Availability

12.2XNE

Please see Cisco IOS-XE Software Availability

Please see Cisco IOS-XE Software Availability

12.2XNF

Please see Cisco IOS-XE Software Availability

Please see Cisco IOS-XE Software Availability

12.2XO

Not Vulnerable

Not Vulnerable

12.2XQ

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XR

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.Releases up to and including 12.2(4)XR are not vulnerable.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XS

Not Vulnerable

Not Vulnerable

12.2XT

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XU

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XV

Not Vulnerable

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2XW

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2YA

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2YB

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YC

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YD

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YE

Not Vulnerable

Not Vulnerable

12.2YF

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YG

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YH

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YJ

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YK

Not Vulnerable

Not Vulnerable

12.2YL

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YM

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2YN

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YO

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YP

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.Releases up to and including 12.2(8)YP are not vulnerable.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2YQ

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YR

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YS

Not Vulnerable

Not Vulnerable

12.2YT

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YU

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YV

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YW

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YX

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YY

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2YZ

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2ZA

Not Vulnerable

Vulnerable; first fixed in 12.2SXF

12.2ZB

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2ZC

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2ZD

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2ZE

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2ZF

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2ZG

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2ZH

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.2ZJ

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2ZL

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2ZP

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2ZU

Not Vulnerable

Vulnerable; first fixed in 12.2SXH

12.2ZX

Not Vulnerable

Vulnerable; migrate to any release in 12.2SRE

12.2ZY

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.2ZYA

Not Vulnerable

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Affected 12.3-Based Releases

First Fixed Release for this Advisory

First Fixed Release for all Advisories in 24 March 2010 Bundle Publication

12.3

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3B

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3BC

Vulnerable; migrate to any release in 12.2SCB

Vulnerable; first fixed in 12.2SCB

12.3BW

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3EU

Not Vulnerable

Not Vulnerable

12.3JA

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Releases prior to 12.3(11)JA5 are vulnerable, release 12.3(11)JA5 and later are not vulnerable

12.3JEA

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Releases prior to 12.3(8)JEA4 are vulnerable, release 12.3(8)JEA4 and later are not vulnerable

12.3JEB

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Releases prior to 12.3(8)JEB2 are vulnerable, release 12.3(8)JEB2 and later are not vulnerable

12.3JEC

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.3JED

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.3JK

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3JL

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.3JX

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.3T

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3TPC

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.3VA

Not Vulnerable

Not Vulnerable

12.3XA

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3XB

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.3XC

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3XD

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3XE

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; first fixed in 12.4

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3XF

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.3XG

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3XI

Note: Releases prior to 12.3(7)XI11 are vulnerable, release 12.3(7)XI11 and later are not vulnerable;

Releases prior to 12.3(7)XI11 are vulnerable, release 12.3(7)XI11 and later are not vulnerable

12.3XJ

Vulnerable; first fixed in 12.4XR

Vulnerable; first fixed in 12.4XR

12.3XK

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3XL

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3XQ

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3XR

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3XS

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3XU

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3XW

Vulnerable; first fixed in 12.4XR

Vulnerable; first fixed in 12.4XR

12.3XX

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3XY

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3XZ

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3YA

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3YD

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3YF

Vulnerable; first fixed in 12.4XR

Vulnerable; first fixed in 12.4XR

12.3YG

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3YH

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3YI

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3YJ

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3YK

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3YM

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3YQ

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3YS

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3YT

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3YU

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.3YX

Vulnerable; first fixed in 12.4XR

Vulnerable; first fixed in 12.4XR

12.3YZ

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.3ZA

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

Affected 12.4-Based Releases

First Fixed Release for this Advisory

First Fixed Release for all Advisories in 24 March 2010 Bundle Publication

12.4

12.4(25c)

15.0(1)M1

15.0(1)M2 ; Available on 26-MAR-10

12.4(25c)

15.0(1)M1

12.4GC

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4JA

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4JDA

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4JDC

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4JDD

12.4(10b)JDD1

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4(10b)JDD1

12.4JHA

Not Vulnerable

Not Vulnerable

12.4JK

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4JL

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4JMA

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Releases prior to 12.4(3g)JMA2 are vulnerable, release 12.4(3g)JMA2 and later are not vulnerable

12.4JMB

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4JX

Vulnerable; first fixed in 12.4JA

Vulnerable; first fixed in 12.4JA

12.4MD

12.4(11)MD10

12.4(15)MD4 12.4(24)MD

12.4(24)MD

12.4MDA

12.4(22)MDA2

12.4(22)MDA2

12.4MR

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4SW

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4T

12.4(22)T3

12.4(20)T4

12.4(15)T10

12.4(24)T2

12.4(15)T12

12.4(20)T5

12.4(24)T3; Available on 26-MAR-10

12.4(22)T4

12.4XA

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XB

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XC

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XD

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XE

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XF

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XG

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XJ

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XK

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XL

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4XM

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XN

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4XP

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4XQ

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XR

12.4(22)XR3

12.4(22)XR3

12.4XT

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XV

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4XW

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XY

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4XZ

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4YA

Vulnerable; migrate to any release in 15.0M or a fixed 12.4T release.

Vulnerable; migrate to any release in 15.0M or a fixed 12.4 release.

12.4YB

12.4(22)YB5

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4YD

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

12.4YE

12.4(22)YE2

12.4(24)YE

12.4(22)YE2

12.4(24)YE

12.4YG

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

Affected 15.0-Based Releases

First Fixed Release for this Advisory

First Fixed Release for all Advisories in 24 March 2010 Bundle Publication

There are no affected 15.0 based releases

Affected 15.1-Based Releases

First Fixed Release for this Advisory

First Fixed Release for all Advisories in 24 March 2010 Bundle Publication

There are no affected 15.1 based releases

Cisco IOS-XE Software

IOS-XE Release

First Fixed Release

2.1.x

Not Vulnerable

2.2.x

Not Vulnerable

2.3.x

Not Vulnerable

2.4.x

Not Vulnerable

2.5.x

Not Vulnerable

2.6.x

Not Vulnerable


Workarounds

There are no workarounds to mitigate this vulnerability other than disabling the specific features that make a device vulnerable, if feasible.

Additionally, allowing only legitimate devices to connect to affected devices will help limit exposure to this vulnerability. Refer to the Control Plane Policing and Configuring Infrastructure Access Lists (iACLs) subsections below for further details. Since a TCP three-way handshake is not required, to increase effectiveness, the mitigation must be coupled with anti-spoofing measures on the network edge.

Specific mitigations for BGP are discussed below in the BGP Considerations subsection.

Additional mitigations that can be deployed on Cisco devices within the network are available in the companion document "Cisco Applied Mitigation Bulletin: Identifying and Mitigating Exploitation of the Cisco IOS Software Crafted TCP Packet Denial of Service Vulnerability", which is available at the following location: http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20100324-tcp.

Configurations Using a Specific TCP Window Size

Not setting a specific TCP receive window size can be accomplished by removing the ip tcp window-size command from the configuration.

Configurations Using Path MTU Discovery

PMTUD may be disabled in some of the Cisco IOS Software features that make use of PMTUD. The specific command to use to disable PMTUD varies depending on the specific feature:

  • TCP over IPv4: removing the ip tcp path-mtu-discovery command from the configuration will disable PMTUD for TCP over IPv4 sessions that originate on the device.
  • TCP over IPv6: PMTUD is enabled by default for IPV6 and cannot be disabled.
  • BGP: if BGP is configured on a recent version of Cisco IOS Software that enables PMTUD for BGP sessions, PMTUD can be disabled for all BGP sessions with the no bgp transport path-mtu-discovery command in router configuration mode (Cisco IOS Release 12.2(33)SRA, 12.2(31)SB, 12.2(33)SXH, 12.4(20)T, and later releases).

Configurations Using Stateful NAT with TCP as the Transport Protocol

SNAT can be disabled by removing the ip nat Stateful id command from the configuration.

Control Plane Policing

For devices that need to offer TCP services, it is possible to use Control Plane Policing (CoPP) to block TCP traffic to the device from untrusted sources. Cisco IOS Releases 12.0S, 12.2SX, 12.2S, 12.3T, 12.4, and 12.4T support the CoPP feature. CoPP may be configured on a device to protect the management and control planes to minimize the risk and effectiveness of direct infrastructure attacks by explicitly permitting only authorized traffic sent to infrastructure devices in accordance with existing security policies and configurations. The following example can be adapted to specific network configurations:


!-- The 192.168.1.0/24 network and the 172.16.1.1 host are trusted.
!-- Everything else is not trusted. The following access list is used
!-- to determine what traffic needs to be dropped by a control plane
!-- policy (the CoPP feature.) If the access list matches (permit)
!-- then traffic will be dropped and if the access list does not
!-- match (deny) then traffic will be processed by the router.
!-- Note that TCP ports 22 and 23 are just examples; this configuration
!-- needs to be expanded to include all used TCP ports.
access-list 100 deny tcp 192.168.1.0 0.0.0.255 any eq 22
access-list 100 deny tcp 192.168.1.0 0.0.0.255 any eq 23
access-list 100 deny tcp host 172.16.1.1 any eq 22
access-list 100 deny tcp host 172.16.1.1 any eq 23
access-list 100 permit tcp any any


!-- Permit (Police or Drop)/Deny (Allow) all other Layer3 and Layer4
!-- traffic in accordance with existing security policies and
!-- configurations for traffic that is authorized to be sent
!-- to infrastructure devices.
!-- Create a Class-Map for traffic to be policed by
!-- the CoPP feature.
class-map match-all drop-tcp-class
  match access-group 100


!-- Create a Policy-Map that will be applied to the
!-- Control-Plane of the device, and add the "drop-tcp-traffic"
!-- class map.
policy-map control-plane-policy
 class drop-tcp-class
  drop


!-- Apply the Policy-Map to the Control-Plane of the
!-- device.
control-plane
 service-policy input control-plane-policy

warning Warning: Because a TCP three-way handshake is not required to exploit this vulnerability, it is possible to easily spoof the IP address of the sender, which may defeat access control lists (ACLs) that permit communication to these ports from trusted IP addresses.

In the above CoPP example, the access control entries (ACEs) that match the potential exploit packets with the "permit" action result in these packets being discarded by the policy-map "drop" function, while packets that match the "deny" action (not shown) are not affected by the policy-map drop function. Additional information on the configuration and use of the CoPP feature can be found at http://www.cisco.com/web/about/security/intelligence/coppwp_gs.html and http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gtrtlimt.html.

Configuring Infrastructure Access Lists (iACLs)

Although it is often difficult to block traffic transiting your network, it is possible to identify traffic that should never be allowed to target your infrastructure devices and block that traffic at the border of your network. Infrastructure ACLs are considered a network security best practice and should be considered as a long-term addition to good network security as well as a workaround for this specific vulnerability. The white paper entitled "Protecting Your Core: Infrastructure Protection Access Control Lists" presents guidelines and recommended deployment techniques for infrastructure protection ACLs:

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_paper09186a00801afc76.shtml

BGP Considerations

BTSH/GTSM can help prevent exploitation of this vulnerability via the BGP port because packets coming from devices that do not pass the TTL check configured via BTSH are dropped before any TCP processing takes place. For information on BTSH refer to: http://www.cisco.com/en/US/docs/ios/12_3t/12_3t7/feature/guide/gt_btsh.html.

MD5 authentication for BGP peering sessions can also help prevent exploitation via the BGP port because the MD5 hash in an attack packet is checked before processing the crafted TCP option. For a detailed discussion on how to configure BGP, refer to the following document: http://www.cisco.com/en/US/docs/ios/12_0/np1/configuration/guide/1cbgp.html.

Obtaining Fixed Software

Cisco has released free software updates that address these vulnerabilities. Prior to deploying software, customers should consult their maintenance provider or check the software for feature set compatibility and known issues specific to their environment.

Customers may only install and expect support for the feature sets they have purchased. By installing, downloading, accessing or otherwise using such software upgrades, customers agree to be bound by the terms of Cisco's software license terms found at http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html , or as otherwise set forth at Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml .

Do not contact psirt@cisco.com or security-alert@cisco.com for software upgrades.

Customers with Service Contracts

Customers with contracts should obtain upgraded software through their regular update channels. For most customers, this means that upgrades should be obtained through the Software Center on Cisco's worldwide website at http://www.cisco.com.

Customers with Service Contracts

Customers with contracts should obtain upgraded software through their regular update channels. For most customers, upgrades should be obtained through the Software Navigator on Cisco.com at http://www.cisco.com/cisco/software/navigator.html.

Customers Using Third-Party Support Organizations

Customers whose Cisco products are provided or maintained through prior or existing agreements with third-party support organizations, such as Cisco Partners, authorized resellers, or service providers should contact that support organization for guidance and assistance with the appropriate course of action in regards to this advisory.

The effectiveness of any workaround or fix is dependent on specific customer situations, such as product mix, network topology, traffic behavior, and organizational mission. Due to the variety of affected products and releases, customers should consult with their service provider or support organization to ensure any applied workaround or fix is the most appropriate for use in the intended network before it is deployed.

Customers Without Service Contracts

Customers who purchase direct from Cisco but do not hold a Cisco service contract, and customers who purchase through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should acquire upgrades by contacting the Cisco Technical Assistance Center (TAC). TAC contacts are as follows.

  • +1 800 553 2447 (toll free from within North America)
  • +1 408 526 7209 (toll call from anywhere in the world)
  • e-mail: tac@cisco.com

Customers should have their product serial number available and be prepared to give the URL of this notice as evidence of entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC.

Refer to http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html for additional TAC contact information, including localized telephone numbers, and instructions and e-mail addresses for use in various languages.

Exploitation and Public Announcements

The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.

This vulnerability was discovered during the resolution of customer service requests.

Status of This Notice: Final

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.

A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.


Distribution

This advisory is posted on Cisco's worldwide website at:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100324-tcp

In addition to worldwide web posting, a text version of this notice is clear-signed with the Cisco PSIRT PGP key and is posted to the following e-mail and Usenet news recipients.

  • cust-security-announce@cisco.com
  • first-bulletins@lists.first.org
  • bugtraq@securityfocus.com
  • vulnwatch@vulnwatch.org
  • cisco@spot.colorado.edu
  • cisco-nsp@puck.nether.net
  • full-disclosure@lists.grok.org.uk
  • comp.dcom.sys.cisco@newsgate.cisco.com

Future updates of this advisory, if any, will be placed on Cisco's worldwide website, but may or may not be actively announced on mailing lists or newsgroups. Users concerned about this problem are encouraged to check the above URL for any updates.


Revision History

Revision 1.0

2010-March-24

Initial public release

Cisco Security Procedures

Complete information on reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco, is available on Cisco's worldwide website at http://www.cisco.com/web/about/security/psirt/security_vulnerability_policy.html. This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at http://www.cisco.com/go/psirt.


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