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Cisco Security Advisory

Multiple DLSw Denial of Service Vulnerabilities in Cisco IOS

Advisory ID: cisco-sa-20080326-dlsw

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080326-dlsw

Revision 1.5

For Public Release 2008 March 26 16:00  UTC (GMT)


Summary

Cisco IOS contains multiple vulnerabilities in the Data-link Switching (DLSw) feature that may result in a reload or memory leaks when processing specially crafted UDP or IP Protocol 91 packets.

Cisco has released free software updates that address these vulnerabilities. Workarounds are available to mitigate the effects of these vulnerabilities.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080326-dlsw.

Note:  The March 26, 2008 publication includes five Security Advisories. The Advisories all affect Cisco's Internetwork Operating System (IOS). Each Advisory lists the releases that correct the vulnerability described in the Advisory, and the Advisories also detail the releases that correct the vulnerabilities in all five Advisories.

Individual publication links are listed below:

Affected Products

Vulnerable Products

This security advisory applies to all Cisco products that run any version of affected Cisco IOS software configured for DLSw. Systems that contain the DLSw feature, but do not have it enabled, are not affected.

Routers enabled for DLSw contain a line in the configuration defining a local DLSw peer. This configuration can be observed by issuing the command show running-config. Systems configured for DLSw contain lines similar to the following:

dlsw local-peer

or

dlsw local-peer peer-id <IP address>

Any version of Cisco IOS prior to the versions which are listed in the Software Versions and Fixes section below is vulnerable.

To determine the version of Cisco IOS software running on a Cisco product, log in to the device and issue the show version command to display the system banner. Cisco IOS Software will identify itself as "Internetwork Operating System Software" or simply "IOS". On the next line of output, the image name will be displayed between parentheses, followed by "Version" and the IOS release name. Other Cisco devices will not have the show version command or will give different output.

The following example identifies a Cisco product running Cisco IOS Software Release 12.3(6) with an installed image name of C3640-IS-M:

Cisco Internetwork Operating System Software
IOS (tm) 3600 Software (C3640-IS-M), Version 12.3(6), RELEASE SOFTWARE (fc3)

The next example shows a product running Cisco IOS Software Release 12.3(11)T3 with an image name of C3845-ADVIPSERVICESK9-M:

Cisco IOS Software, 3800 Software (C3845-ADVIPSERVICESK9-M), Version 12.3(11)T3, RELEASE SOFTWARE (fc4)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2005 by Cisco Systems, Inc.

Additional information about Cisco IOS release naming can be found at http://www.cisco.com/warp/public/620/1.html.

Products Confirmed Not Vulnerable

Cisco IOS devices that are not configured for DLSw are not vulnerable.

No other Cisco products are currently known to be affected by these vulnerabilities.

Details

Data-link switching (DLSw) provides a means of transporting IBM Systems Network Architecture (SNA) and network basic input/output system (NetBIOS) traffic over an IP network. Cisco implementation of DLSw also uses UDP port 2067 and IP Protocol 91 for Fast Sequenced Transport (FST).

Multiple vulnerabilities exists in Cisco IOS when processing UDP and IP protocol 91 packets. These vulnerabilities do not affect TCP packet processing. A successful exploitation may result in a reload of the system or a memory leak on the device, leading to a denial of service (DoS) condition.

Cisco IOS devices configured for DLSw with dlsw local-peer automatically listen for IP protocol 91 packets. A Cisco IOS device that is configured for DLSw with the dlsw local-peer peer-id <IP-address> command listen for IP protocol 91 packets and UDP port 2067.

Cisco IOS devices listen to IP protocol 91 packets when DLSw is configured. However, it is only used if DLSw is configured for Fast Sequenced Transport (FST). A DLSw FST peer configuration will contain the following line:

dlsw remote-peer 0 fst <ip-address>

It is possible to disable UDP processing in DLSw with the dlsw udp-disable command. However, disabling UDP only prevents the sending of UDP packets, it does not prevent the device from receiving and processing incoming UDP packets.

These vulnerabilities are documented in Cisco Bug ID CSCsk73104 ( registered customers only) and have been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2008-1152.

Vulnerability Scoring Details

Cisco has provided scores for the vulnerabilities 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 .

CSCsk73104 - Handling of malformed packets by DLSW

Calculate the environmental score of CSCsk73104

CVSS Base Score - 7.8

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Low

None

None

None

Complete

CVSS Temporal Score - 6.4

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

Impact

Successful exploitation of these vulnerabilities may result in the reload of the device or memory leaks, leading to a DoS condition.

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" column of the table. The "Recommended Release" column indicates the releases which have fixes for all the published vulnerabilities at the time of this Advisory. A device running a release in the given train that is earlier than the release in a specific column (less than the First Fixed Release) is known to be vulnerable. Cisco recommends upgrading to a release equal to or later than the release in the "Recommended Releases" column of the table.

Major Release

Availability of Repaired Releases

Affected 12.0-Based Releases

First Fixed Release

Recommended Release

12.0

Vulnerable; first fixed in 12.3

12.3(26)

12.0DA

Releases prior to 12.0(8)DA3 are vulnerable, release 12.0(8)DA3 and later are not vulnerable; migrate to any release in 12.2DA

 

12.0DB

Releases prior to 12.0(7)DB are vulnerable, release 12.0(7)DB and later are not vulnerable; first fixed in 12.4

12.4(18a)

12.0DC

Releases prior to 12.0(7)DC are vulnerable, release 12.0(7)DC and later are not vulnerable; first fixed in 12.4

12.4(18a)

12.0S

Releases prior to 12.0(17)S5 are vulnerable, release 12.0(17)S5 and later are not vulnerable;

 

12.0SC

Not Vulnerable

 

12.0SL

Not Vulnerable

 

12.0SP

Not Vulnerable

 

12.0ST

Not Vulnerable

 

12.0SX

Not Vulnerable

 

12.0SY

Not Vulnerable

 

12.0SZ

Not Vulnerable

 

12.0T

Vulnerable; first fixed in 12.3

12.3(26)

12.0W

Vulnerable; contact TAC

12.0(3c)W5(8)

12.0WC

Vulnerable; contact TAC

 

12.0WT

Not Vulnerable

 

12.0XA

Vulnerable; first fixed in 12.3

12.3(26)

12.0XB

Not Vulnerable

 

12.0XC

Releases prior to 12.0(2)XC2 are vulnerable, release 12.0(2)XC2 and later are not vulnerable; first fixed in 12.3

12.3(26)

12.0XD

Vulnerable; first fixed in 12.3

12.3(26)

12.0XE

Vulnerable; first fixed in 12.1E

 

12.0XF

Not Vulnerable

 

12.0XG

Vulnerable; first fixed in 12.3

12.3(26)

12.0XH

Vulnerable; first fixed in 12.3

12.3(26)

12.0XI

Releases prior to 12.0(4)XI2 are vulnerable, release 12.0(4)XI2 and later are not vulnerable; first fixed in 12.3

12.3(26)

12.0XJ

Releases prior to 12.0(4)XJ5 are vulnerable, release 12.0(4)XJ5 and later are not vulnerable; first fixed in 12.3

12.3(26)

12.0XK

Vulnerable; first fixed in 12.3

12.3(26)

12.0XL

Not Vulnerable

 

12.0XM

Not Vulnerable

 

12.0XN

Vulnerable; first fixed in 12.3

12.3(26)

12.0XQ

Vulnerable; first fixed in 12.3

12.3(26)

12.0XR

Vulnerable; first fixed in 12.3

12.3(26)

12.0XS

Not Vulnerable

 

12.0XV

Not Vulnerable

 

12.0XW

Not Vulnerable

 

Affected 12.1-Based Releases

First Fixed Release

Recommended Release

12.1

Vulnerable; first fixed in 12.3

12.3(26)

12.1AA

Vulnerable; first fixed in 12.3

12.3(26)

12.1AX

Not Vulnerable

 

12.1AY

Releases prior to 12.1(22)AY1 are vulnerable, release 12.1(22)AY1 and later are not vulnerable;

12.1(22)EA11

12.1AZ

Not Vulnerable

 

12.1CX

Not Vulnerable

 

12.1DA

Not Vulnerable

 

12.1DB

Releases prior to 12.1(4)DB1 are vulnerable, release 12.1(4)DB1 and later are not vulnerable; first fixed in 12.4

12.4(18a)

12.1DC

Releases prior to 12.1(4)DC2 are vulnerable, release 12.1(4)DC2 and later are not vulnerable; first fixed in 12.4

12.4(18a)

12.1E

12.1(27b)E4

 

12.1EA

Releases prior to 12.1(11)EA1 are vulnerable, release 12.1(11)EA1 and later are not vulnerable;

12.1(22)EA11

12.1EB

Not Vulnerable

 

12.1EC

Vulnerable; migrate to any release in 12.2BC

12.3(23)BC1

12.1EO

Not Vulnerable

 

12.1EU

Not Vulnerable

 

12.1EV

Not Vulnerable

 

12.1EW

Not Vulnerable

 

12.1EX

Vulnerable; first fixed in 12.1E

 

12.1EY

Not Vulnerable

 

12.1EZ

Vulnerable; first fixed in 12.1E

 

12.1GA

Vulnerable; first fixed in 12.3

12.3(26)

12.1GB

Vulnerable; first fixed in 12.3

12.3(26)

12.1T

Vulnerable; first fixed in 12.3

12.3(26)

12.1XA

Vulnerable; first fixed in 12.3

12.3(26)

12.1XB

Not Vulnerable

 

12.1XC

Vulnerable; first fixed in 12.3

12.3(26)

12.1XD

Vulnerable; first fixed in 12.3

12.3(26)

12.1XE

Not Vulnerable

 

12.1XF

Not Vulnerable

 

12.1XG

Vulnerable; first fixed in 12.3

12.3(26)

12.1XH

Vulnerable; first fixed in 12.3

12.3(26)

12.1XI

Vulnerable; first fixed in 12.3

12.3(26)

12.1XJ

Vulnerable; first fixed in 12.3

12.3(26)

12.1XK

Not Vulnerable

 

12.1XL

Not Vulnerable

 

12.1XM

Vulnerable; first fixed in 12.3

12.3(26)

12.1XN

Not Vulnerable

 

12.1XO

Not Vulnerable

 

12.1XP

Vulnerable; first fixed in 12.3

12.3(26)

12.1XQ

Vulnerable; first fixed in 12.3

12.3(26)

12.1XR

Not Vulnerable

 

12.1XS

Vulnerable; first fixed in 12.3

12.3(26)

12.1XT

Releases prior to 12.1(3)XT2 are vulnerable, release 12.1(3)XT2 and later are not vulnerable; first fixed in 12.3

12.3(26)

12.1XU

Not Vulnerable

 

12.1XV

Releases prior to 12.1(5)XV1 are vulnerable, release 12.1(5)XV1 and later are not vulnerable; first fixed in 12.3

12.3(26)

12.1XW

Vulnerable; first fixed in 12.3

12.3(26)

12.1XX

Vulnerable; first fixed in 12.3

12.3(26)

12.1XY

Vulnerable; first fixed in 12.3

12.3(26)

12.1XZ

Vulnerable; first fixed in 12.3

12.3(26)

12.1YA

Vulnerable; first fixed in 12.3

12.3(26)

12.1YB

Vulnerable; first fixed in 12.3

12.3(26)

12.1YC

Not Vulnerable

 

12.1YD

Vulnerable; first fixed in 12.3

12.3(26)

12.1YE

Releases prior to 12.1(5)YE1 are vulnerable, release 12.1(5)YE1 and later are not vulnerable; first fixed in 12.3

12.3(26)

12.1YF

Not Vulnerable

 

12.1YG

Not Vulnerable

 

12.1YH

Not Vulnerable

 

12.1YI

Vulnerable; first fixed in 12.3

12.3(26)

12.1YJ

Not Vulnerable

 

Affected 12.2-Based Releases

First Fixed Release

Recommended Release

12.2

Vulnerable; first fixed in 12.3

12.3(26)

12.2B

Vulnerable; first fixed in 12.4

12.4(18a)

12.2BC

Not Vulnerable

 

12.2BW

Vulnerable; first fixed in 12.3

12.3(26)

12.2BY

Vulnerable; first fixed in 12.4

12.4(18a)

12.2BZ

Not Vulnerable

 

12.2CX

Not Vulnerable

 

12.2CY

Not Vulnerable

 

12.2CZ

Not Vulnerable

 

12.2DA

Not Vulnerable

 

12.2DD

Vulnerable; first fixed in 12.4

12.4(18a)

12.2DX

Vulnerable; first fixed in 12.4

12.4(18a)

12.2EU

Not Vulnerable

 

12.2EW

Not Vulnerable

 

12.2EWA

Not Vulnerable

 

12.2EX

Releases prior to 12.2(20)EX are vulnerable, release 12.2(20)EX and later are not vulnerable; migrate to any release in 12.2SEA

12.2(40)EX1

12.2EY

Not Vulnerable

 

12.2EZ

Not Vulnerable

 

12.2FX

Not Vulnerable

 

12.2FY

Not Vulnerable

 

12.2FZ

Not Vulnerable

 

12.2IXA

Vulnerable; contact TAC

 

12.2IXB

Vulnerable; contact TAC

 

12.2IXC

Vulnerable; contact TAC

 

12.2IXD

Vulnerable; contact TAC

 

12.2IXE

Vulnerable; migrate to any release in 12.2IXF

12.2(18)IXF; Available on 31-MAR-08

12.2JA

Not Vulnerable

 

12.2JK

Not Vulnerable

 

12.2MB

Not Vulnerable

 

12.2MC

12.2(15)MC2h

12.2(15)MC2k

12.2S

12.2(25)S15

12.2(25)S15

12.2SB

12.2(28)SB10

12.2(31)SB9

12.2(33)SB; Available on 31-MAR-2008

12.2(31)SB11

12.2SBC

Vulnerable; first fixed in 12.2SB; Available on 31-MAR-2008

12.2(31)SB11

12.2SCA

Not Vulnerable

 

12.2SE

Not Vulnerable

 

12.2SEA

Not Vulnerable

 

12.2SEB

Not Vulnerable

 

12.2SEC

Not Vulnerable

 

12.2SED

Not Vulnerable

 

12.2SEE

Not Vulnerable

 

12.2SEF

Not Vulnerable

 

12.2SEG

Not Vulnerable

 

12.2SG

12.2(44)SG

12.2(44)SG

12.2SGA

Not Vulnerable

 

12.2SL

Not Vulnerable

 

12.2SM

Not Vulnerable

 

12.2SO

Not Vulnerable

 

12.2SRA

12.2(33)SRA6

12.2(33)SRA7

12.2SRB

12.2(33)SRB3; Available on 07-APR-2008

12.2(33)SRB3; Available on 14-APR-08

12.2SRC

Not Vulnerable

 

12.2SU

Vulnerable; first fixed in 12.4

12.4(18a)

12.2SV

Releases prior to 12.2(29a)SV1 are vulnerable, release 12.2(29a)SV1 and later are not vulnerable; migrate to any release in 12.2SVA

12.2(29b)SV

12.2SVA

Not Vulnerable

 

12.2SVC

Not Vulnerable

 

12.2SVD

Not Vulnerable

 

12.2SW

Releases prior to 12.2(25)SW10 are vulnerable, release 12.2(25)SW10 and later are not vulnerable;

 

12.2SX

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2SXA

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2SXB

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2SXD

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2SXE

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2SXF

12.2(18)SXF12

12.2(18)SXF12a

12.2(18)SXF13

12.2SXH

12.2(33)SXH1

12.2(33)SXH2

12.2SY

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2SZ

Vulnerable; first fixed in 12.2S

12.2(25)S15

12.2(31)SB11

12.2(33)SRC

12.2T

Vulnerable; first fixed in 12.3

12.3(26)

12.2TPC

12.2(8)TPC10d

 

12.2UZ

Not Vulnerable

 

12.2XA

Vulnerable; first fixed in 12.3

12.3(26)

12.2XB

Vulnerable; first fixed in 12.3

12.3(26)

12.2XC

Vulnerable; first fixed in 12.4

12.4(18a)

12.2XD

Vulnerable; first fixed in 12.3

12.3(26)

12.2XE

Not Vulnerable

 

12.2XF

Not Vulnerable

 

12.2XG

Vulnerable; first fixed in 12.3

12.3(26)

12.2XH

Vulnerable; first fixed in 12.3

12.3(26)

12.2XI

Not Vulnerable

 

12.2XJ

Vulnerable; first fixed in 12.3

12.3(26)

12.2XK

Vulnerable; first fixed in 12.3

12.3(26)

12.2XL

Vulnerable; first fixed in 12.3

12.3(26)

12.2XM

Vulnerable; first fixed in 12.3

12.3(26)

12.2XN

12.2(33)XN1

12.3(26)

12.2XO

Not Vulnerable

 

12.2XQ

Vulnerable; first fixed in 12.3

12.3(26)

12.2XR

Not Vulnerable

 

12.2XS

Not Vulnerable

 

12.2XT

Vulnerable; first fixed in 12.3

12.3(26)

12.2XU

Vulnerable; first fixed in 12.3

12.3(26)

12.2XV

Vulnerable; first fixed in 12.3

12.3(26)

12.2XW

Vulnerable; first fixed in 12.3

12.3(26)

12.2YA

Releases prior to 12.2(4)YA8 are vulnerable, release 12.2(4)YA8 and later are not vulnerable; first fixed in 12.3

12.3(26)

12.2YB

Vulnerable; first fixed in 12.3

12.3(26)

12.2YC

Vulnerable; first fixed in 12.3

12.3(26)

12.2YD

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YE

Vulnerable; first fixed in 12.2S

12.2(25)S15

12.2(31)SB11

12.2(33)SRC

12.2YF

Vulnerable; first fixed in 12.3

12.3(26)

12.2YG

Not Vulnerable

 

12.2YH

Vulnerable; first fixed in 12.3

12.3(26)

12.2YJ

Releases prior to 12.2(8)YJ1 are vulnerable, release 12.2(8)YJ1 and later are not vulnerable; first fixed in 12.3

12.3(26)

12.2YK

Not Vulnerable

 

12.2YL

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YM

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YN

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YO

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2YP

Not Vulnerable

 

12.2YQ

Not Vulnerable

 

12.2YR

Not Vulnerable

 

12.2YS

Not Vulnerable

 

12.2YT

Vulnerable; first fixed in 12.3

12.3(26)

12.2YU

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YV

Releases prior to 12.2(11)YV1 are vulnerable, release 12.2(11)YV1 and later are not vulnerable; first fixed in 12.4

12.4(18a)

12.2YW

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YX

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YY

Vulnerable; first fixed in 12.4

12.4(18a)

12.2YZ

Vulnerable; first fixed in 12.2S

12.2(25)S15

12.2(31)SB11

12.2(33)SRC

12.2ZA

Vulnerable; first fixed in 12.2SXF

12.2(18)SXF13

12.2ZB

Vulnerable; first fixed in 12.4

12.4(18a)

12.2ZC

Not Vulnerable

 

12.2ZD

Vulnerable; contact TAC

 

12.2ZE

Vulnerable; first fixed in 12.3

12.3(26)

12.2ZF

Vulnerable; first fixed in 12.4

12.4(18a)

12.2ZG

Not Vulnerable

 

12.2ZH

Releases prior to 12.2(13)ZH6 are vulnerable, release 12.2(13)ZH6 and later are not vulnerable; first fixed in 12.4

12.2(13)ZH11

12.2ZJ

Vulnerable; first fixed in 12.4

12.4(18a)

12.2ZL

Vulnerable; first fixed in 12.4

12.4(15)T4

12.4(18a)

12.2ZP

Not Vulnerable

 

12.2ZU

Vulnerable; first fixed in 12.2SXH

12.2(33)SXH2

12.2ZY

12.2(18)ZY2

12.2(18)ZY2

Affected 12.3-Based Releases

First Fixed Release

Recommended Release

12.3

12.3(24)

12.3(26)

12.3B

Vulnerable; first fixed in 12.4

12.4(18a)

12.3BC

Not Vulnerable

 

12.3BW

Vulnerable; first fixed in 12.4

12.4(18a)

12.3EU

Not Vulnerable

 

12.3JA

Not Vulnerable

 

12.3JEA

Not Vulnerable

 

12.3JEB

Not Vulnerable

 

12.3JEC

Not Vulnerable

 

12.3JK

Releases prior to 12.3(8)JK1 are vulnerable, release 12.3(8)JK1 and later are not vulnerable;

12.3(8)JK1

12.3JL

Not Vulnerable

 

12.3JX

Not Vulnerable

 

12.3T

Vulnerable; first fixed in 12.4

12.4(18a)

12.3TPC

Not Vulnerable

 

12.3VA

Vulnerable; contact TAC

 

12.3XA

12.3(2)XA7; Available on 31-MAR-2008

12.3(2)XA7; Available on 31-MAR-08

12.3XB

Vulnerable; first fixed in 12.4

12.4(18a)

12.3XC

12.3(2)XC5

12.4(15)T4

12.4(18a)

12.3XD

Vulnerable; first fixed in 12.4

12.4(18a)

12.3XE

12.3(2)XE6; Available on 31-MAR-2008

12.4(15)T4

12.4(18a)

12.3XF

Vulnerable; first fixed in 12.4

12.4(18a)

12.3XG

Vulnerable; first fixed in 12.3YG; Available on 16-JUN-2008

12.4(15)T4

12.4(18a)

12.3XH

Vulnerable; first fixed in 12.4

12.4(18a)

12.3XI

12.3(7)XI11; Available on 18-SEP-2008

 

12.3XJ

Vulnerable; first fixed in 12.3YX

12.3(14)YX11

12.4(15)T4

12.3XK

Vulnerable; first fixed in 12.4

12.4(18a)

12.3XQ

Vulnerable; first fixed in 12.4

12.4(18a)

12.3XR

12.3(7)XR8; Available on 31-MAR-2008

12.3(7)XR8; Available on 31-MAR-08

12.3XS

Not Vulnerable

 

12.3XU

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3XW

Vulnerable; first fixed in 12.3YX

12.3(14)YX11

12.4(15)T4

12.3XY

Not Vulnerable

 

12.3YA

Not Vulnerable

 

12.3YD

Not Vulnerable

 

12.3YF

Vulnerable; first fixed in 12.3YX

12.3(14)YX11

12.4(15)T4

12.3YG

12.3(8)YG7; Available on 16-JUN-2008

12.4(15)T4

12.3YH

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3YI

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3YJ

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3YK

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3YM

12.3(14)YM12

12.3(14)YM12

12.3YQ

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3YS

12.3(11)YS3; Available on 31-MAR-2008

12.4(15)T4

12.3YT

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.3YU

Vulnerable; first fixed in 12.4XB

 

12.3YX

12.3(14)YX11

12.3(14)YX11

12.3YZ

12.3(11)YZ3

 

Affected 12.4-Based Releases

First Fixed Release

Recommended Release

12.4

12.4(10c)

12.4(13e)

12.4(16b)

12.4(17)

12.4(3h)

12.4(8d)

12.4(18a)

12.4JA

Not Vulnerable

 

12.4JK

Not Vulnerable

 

12.4JMA

Not Vulnerable

 

12.4JMB

Not Vulnerable

 

12.4JMC

Not Vulnerable

 

12.4JX

Not Vulnerable

 

12.4MD

Not Vulnerable

 

12.4MR

Not Vulnerable

 

12.4SW

Vulnerable; contact TAC

12.4(15)SW

12.4T

12.4(15)T2

12.4(6)T10

12.4(9)T7

12.4(15)T4

12.4XA

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.4XB

12.4(2)XB6

 

12.4XC

Vulnerable; contact TAC

 

12.4XD

12.4(4)XD10

12.4(4)XD10

12.4XE

12.4(6)XE2

12.4(15)T4

12.4XF

Not Vulnerable

 

12.4XG

12.4(9)XG2

12.4(9)XG2

12.4XJ

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.4XK

Vulnerable; first fixed in 12.4T

12.4(15)T4

12.4XL

12.4(15)XL2

12.4(15)XL2

12.4XM

Not Vulnerable

 

12.4XN

Not Vulnerable

 

12.4XT

12.4(6)XT2

12.4(6)XT2

12.4XV

12.4(11)XV

 

12.4XW

Vulnerable; contact TAC

12.4(11)XW6

12.4XY

Not Vulnerable

 

A special patch for Cisco IOS Software Modularity is also available for 12.2(18)SXF11 and can be downloaded from the Cisco IOS Software Modularity Patch Navigator at http://tools.cisco.com/swdf/ionpn/jsp/result.jsp?s_tarballWild=mp001-p.122-18.SXF11&reqType=cWork.


Workarounds

The workaround consists of filtering UDP packets to port 2067 and IP protocol 91 packets. Filters can be applied at network boundaries to filter all IP protocol 91 packets and UDP packets to port 2067 or can be applied on individual affected devices to permit such traffic only from trusted peer IP addresses. However, since both of the protocols are connectionless, it is possible for an attacker to spoof malformed packets from legitimate peer IP addresses.

As soon as DLSw is configured, the Cisco IOS device begins listening on IP protocol 91. However, this protocol is only used if DLSw is configured for Fast Sequenced Transport (FST). A DLSw FST peer configuration will contain the following line:

dlsw remote-peer 0 fst <ip-address>

If FST is used, filtering IP protocol 91 will break the operation, so filters need to permit protocol 91 traffic from legitimate peer IP addresses.

It is possible to disable UDP processing in DLSw with the dlsw udp-disable command. However, disabling UDP only prevents the sending of UDP packets, it does not prevent the receiving and processing of incoming UDP packets. To protect a vulnerable device from malicious packets via UDP port 2067, both of the following actions must be taken:

  1. Disable UDP outgoing packets with the "dlsw udp-disable" command, AND
  2. Filter UDP 2067 in the vulnerable device using infrastructure ACL.

Additional mitigation techniques that can be deployed on Cisco devices within the network are available in the Cisco Applied Mitigation Bulletin companion document for this advisory:

http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20080326-dlsw

Using Control Plane Policing on Affected Devices

Control Plane Policing (CoPP) can be used to block untrusted DLSw traffic to the device. Cisco IOS software 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, which uses 192.168.100.1 to represent a trusted host, can be adapted to your network. If FST is not used, protocol 91 may be completely filtered. Additionally, if UDP is disabled with the dlsw udp-disable command, UDP port 2067 may also be completely filtered.


!--- Deny DLSw traffic from trusted hosts to all IP addresses
!--- configured on all interfaces of the affected device so that
!--- it will be allowed by the CoPP feature


access-list 111 deny udp host 192.168.100.1 any eq 2067
access-list 111 deny 91 host 192.168.100.1 any


!--- Permit all other DLSw traffic sent to all IP addresses
!--- configured on all interfaces of the affected device so that it
!--- will be policed and dropped by the CoPP feature


access-list 111 permit udp any any eq 2067
access-list 111 permit 91 any any 


!--- Permit (Police or Drop)/Deny (Allow) all other Layer 3 and Layer 4
!--- 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-DLSw-class
 match access-group 111


!--- Create a Policy-Map that will be applied to the
!--- Control-Plane of the device.


policy-map drop-DLSw-traffic
 class drop-DLSw-class
  drop


!--- Apply the Policy-Map to the Control-Plane of the
!--- device


control-plane
 service-policy input drop-DLSw-traffic

In the above CoPP example, the access control entries (ACEs) which 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. Please note that in the Cisco IOS 12.2S and 12.0S trains the policy-map syntax is different:

policy-map drop-DLSw-traffic
 class drop-DLSw-class
  police 32000 1500 1500 conform-action drop exceed-action drop

Additional information on the configuration and use of the CoPP feature is available at http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6586/ps6642/prod_white_paper0900aecd804fa16a.html and http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gtrtlimt.html.

Using Infrastructure ACLs at Network Boundary

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. iACLs are 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 iACL example shown below should be included as part of the deployed infrastructure access-list that will protect all devices with IP addresses in the infrastructure IP address range. If FST is not used, protocol 91 may be completely filtered. Additionally, if UDP is disabled with the dlsw udp-disable command, UDP port 2067 may also be completely filtered.


!--- Permit DLSw (UDP port 2067 and IP protocol 91) packets
!--- from trusted hosts destined to infrastructure addresses.


access-list 150 permit udp TRUSTED_HOSTS MASK INFRASTRUCTURE_ADDRESSES MASK eq 2067

access-list 150 permit 91 TRUSTED_HOSTS MASK INFRASTRUCTURE_ADDRESSES MASK 


!--- Deny DLSw (UDP port 2067 and IP protocol 91) packets from 
!--- all other sources destined to infrastructure addresses.


access-list 150 deny udp any INFRASTRUCTURE_ADDRESSES MASK eq 2067
access-list 150 deny 91 any INFRASTRUCTURE_ADDRESSES MASK


!--- Permit/deny all other Layer 3 and Layer 4 traffic in accordance
!--- with existing security policies and configurations
!--- Permit all other traffic to transit the device.


access-list 150 permit ip any any

interface serial 2/0
 ip access-group 150 in

The white paper entitled "Protecting Your Core: Infrastructure Protection Access Control Lists" presents guidelines and recommended deployment techniques for infrastructure protection access lists. This white paper can be obtained at the following link:

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_paper09186a00801a1a55.shtml

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 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/warp/public/687/Directory/DirTAC.shtml 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.

These vulnerabilities were found internally.

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-20080326-dlsw

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-teams@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 1.5

2008-June-26

Updated Summary to remove link and verbiage.

Revision 1.4

2008-April-25

Updated link to the CVSS score of CSCsk73104.

Revision 1.3

2008-Apr-21

Added the specific link for IOS Software Modularity patch

Revision 1.2

2008-Mar-31

Replacing IOS First Fixed Table with correct table -- data visible between 3/28 and 3/31was incorrect

Revision 1.1

2008-Mar-29

Updated Software Table for 12.0S, 12.0SY, 12.0SX and 12.0SZ due to new information on advisory ID cisco-sa-20080326-IPv4IPv6, the March 26th advisory on IPv4IPv6 Dual Stack Routers.

Revision 1.0

2008-Mar-26

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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