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Cisco Security Advisory

Cisco IOS Software H.323 Denial of Service Vulnerability

Advisory ID: cisco-sa-20090923-h323

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20090923-h323

Revision 1.1

For Public Release 2009 September 23 16:00  UTC (GMT)

Related Resources:

View related IPS SignatureView related Applied Mitigation BulletinView related Alert

Summary

The H.323 implementation in Cisco IOS® Software contains a vulnerability that can be exploited remotely to cause a device that is running Cisco IOS Software to reload.

Cisco has released free software updates that address this vulnerability. There are no workarounds to mitigate the vulnerability apart from disabling H.323 if the device that is running Cisco IOS Software does not need to run H.323 for VoIP services.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20090923-h323.

Note: The September 23, 2009, Cisco IOS Security Advisory bundled publication includes eleven Security Advisories. Ten of the advisories address vulnerabilities in Cisco IOS Software, and one advisory addresses a vulnerability in Cisco Unified Communications Manager. Each advisory lists the releases that correct the vulnerability or vulnerabilities detailed in the advisory.

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

http://www.cisco.com/web/about/security/intelligence/Cisco_ERP_ sep09.html

Affected Products

Vulnerable Products

Cisco devices that are running affected Cisco IOS Software versions that are configured to process H.323 messages are affected by this vulnerability. H.323 is not enabled by default.

To determine the Cisco IOS Software device is running H.323 services use the show process cpu | include 323 command, as shown in the following example:

Router#show process cpu | include 323
 249       16000           3       5333  0.00%  0.00%  0.00%   0 CCH323_CT
 250           0           1          0  0.00%  0.00%  0.00%   0 CCH323_DNS
Router# 

Note: Only H.323 listening port TCP 1720 is affected.

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 displays 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 XE and Cisco IOS XR Software are not affected by this vulnerability. No other Cisco products are currently known to be affected by this vulnerability.

Details

H.323 is the ITU standard for real-time multimedia communications and conferencing over packet-based (IP) networks. A subset of the H.323 standard is H.225.0, a standard used for call signalling protocols and media stream packetization over IP networks.

The H.323 implementation in Cisco IOS Software contains a vulnerability. An attacker can exploit this vulnerability remotely by sending an H.323 crafted packet to the affected device that is running Cisco IOS Software. A TCP three-way handshake is needed to exploit this vulnerability.

This vulnerability is documented in Cisco bug ID CSCsz38104 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2009-2866.

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 .

CSCsz38104 - Crafted H323 packets may cause device to reload

Calculate the environmental score of CSCsz38104

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 the vulnerability described in this document may cause the affected device to reload. The issue could be exploited repeatedly to cause an extended 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 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

There are no affected 12.0 based releases.

Affected 12.1-Based Releases

First Fixed Release

Recommended Release

There are no affected 12.1 based releases.

Affected 12.2-Based Releases

First Fixed Release

Recommended Release

12.2

Not Vulnerable

 

12.2B

Vulnerable; first fixed in 12.4

Releases up to and including 12.2(4)B8 are not vulnerable.

12.4(25b)

12.4(23b)

12.2BC

Not Vulnerable

 

12.2BW

Not Vulnerable

 

12.2BX

Vulnerable; first fixed in 12.4

Releases up to and including 12.2(15)BX are not vulnerable.

12.4(25b)

12.4(23b)

12.2BY

Not Vulnerable

 

12.2BZ

Not Vulnerable

 

12.2CX

Not Vulnerable

 

12.2CY

Not Vulnerable

 

12.2CZ

Vulnerable; migrate to 12.2SB

12.2(33)SB7

12.2DA

Not Vulnerable

 

12.2DD

Not Vulnerable

 

12.2DX

Not Vulnerable

 

12.2EW

Not Vulnerable

 

12.2EWA

Not Vulnerable

 

12.2EX

Not Vulnerable

 

12.2EY

Not Vulnerable

 

12.2EZ

Not Vulnerable

 

12.2FX

Not Vulnerable

 

12.2FY

Not Vulnerable

 

12.2FZ

Not Vulnerable

 

12.2IRA

Not Vulnerable

 

12.2IRB

Not Vulnerable

 

12.2IRC

Not Vulnerable

 

12.2IXA

Not Vulnerable

 

12.2IXB

Not Vulnerable

 

12.2IXC

Not Vulnerable

 

12.2IXD

Not Vulnerable

 

12.2IXE

Not Vulnerable

 

12.2IXF

Not Vulnerable

 

12.2IXG

Not Vulnerable

 

12.2IXH

Not Vulnerable

 

12.2JA

Not Vulnerable

 

12.2JK

Not Vulnerable

 

12.2MB

Not Vulnerable

 

12.2MC

Releases up to and including 12.2(15)MC1 are not vulnerable.

Releases 12.2(15)MC2b and later are not vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.2S

Not Vulnerable

 

12.2SB

Not Vulnerable

 

12.2SBC

Not Vulnerable

 

12.2SCA

Not Vulnerable

 

12.2SCB

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

Not Vulnerable

 

12.2SGA

Not Vulnerable

 

12.2SL

Not Vulnerable

 

12.2SM

Not Vulnerable

 

12.2SO

Not Vulnerable

 

12.2SQ

Not Vulnerable

 

12.2SRA

Not Vulnerable

 

12.2SRB

Not Vulnerable

 

12.2SRC

Not Vulnerable

 

12.2SRD

Not Vulnerable

 

12.2STE

Not Vulnerable

 

12.2SU

Not Vulnerable

 

12.2SV

Not Vulnerable

 

12.2SVA

Not Vulnerable

 

12.2SVC

Not Vulnerable

 

12.2SVD

Not Vulnerable

 

12.2SVE

Not Vulnerable

 

12.2SW

Not Vulnerable

 

12.2SX

Not Vulnerable

 

12.2SXA

Not Vulnerable

 

12.2SXB

Not Vulnerable

 

12.2SXD

Not Vulnerable

 

12.2SXE

Not Vulnerable

 

12.2SXF

Not Vulnerable

 

12.2SXH

Not Vulnerable

 

12.2SXI

Not Vulnerable

 

12.2SY

Not Vulnerable

 

12.2SZ

Not Vulnerable

 

12.2T

Vulnerable; first fixed in 12.4

Releases up to and including 12.2(8)T10 are not vulnerable.

12.4(25b)

12.4(23b)

12.2TPC

Not Vulnerable

 

12.2XA

Not Vulnerable

 

12.2XB

Not Vulnerable

 

12.2XC

Not Vulnerable

 

12.2XD

Not Vulnerable

 

12.2XE

Not Vulnerable

 

12.2XF

Not Vulnerable

 

12.2XG

Not Vulnerable

 

12.2XH

Not Vulnerable

 

12.2XI

Not Vulnerable

 

12.2XJ

Not Vulnerable

 

12.2XK

Not Vulnerable

 

12.2XL

Not Vulnerable

 

12.2XM

Not Vulnerable

 

12.2XNA

Not Vulnerable

 

12.2XNB

Not Vulnerable

 

12.2XNC

Not Vulnerable

 

12.2XND

Not Vulnerable

 

12.2XO

Not Vulnerable

 

12.2XQ

Not Vulnerable

 

12.2XR

Not Vulnerable

 

12.2XS

Not Vulnerable

 

12.2XT

Not Vulnerable

 

12.2XU

Not Vulnerable

 

12.2XV

Not Vulnerable

 

12.2XW

Not Vulnerable

 

12.2YA

Not Vulnerable

 

12.2YB

Not Vulnerable

 

12.2YC

Not Vulnerable

 

12.2YD

Not Vulnerable

 

12.2YE

Not Vulnerable

 

12.2YF

Not Vulnerable

 

12.2YG

Not Vulnerable

 

12.2YH

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

 

12.2YK

Not Vulnerable

 

12.2YL

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

 

12.2YM

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.2YN

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

 

12.2YO

Not Vulnerable

 

12.2YP

Not Vulnerable

 

12.2YQ

Not Vulnerable

 

12.2YR

Not Vulnerable

 

12.2YS

Not Vulnerable

 

12.2YT

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

 

12.2YV

Releases prior to 12.2(11)YV1 are vulnerable, release 12.2(11)YV1 and later are not vulnerable

 

12.2YW

Not Vulnerable

 

12.2YX

Not Vulnerable

 

12.2YY

Not Vulnerable

 

12.2YZ

Not Vulnerable

 

12.2ZA

Not Vulnerable

 

12.2ZB

Not Vulnerable

 

12.2ZC

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

 

12.2ZE

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.2ZF

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.2ZG

Not Vulnerable

 

12.2ZH

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.2ZJ

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

 

12.2ZP

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

 

12.2ZU

Not Vulnerable

 

12.2ZX

Not Vulnerable

 

12.2ZY

Not Vulnerable

 

12.2ZYA

Not Vulnerable

 

Affected 12.3-Based Releases

First Fixed Release

Recommended Release

12.3

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3B

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3BC

Not Vulnerable

 

12.3BW

Not Vulnerable

 

12.3EU

Not Vulnerable

 

12.3JA

Not Vulnerable

 

12.3JEA

Not Vulnerable

 

12.3JEB

Not Vulnerable

 

12.3JEC

Not Vulnerable

 

12.3JK

Releases up to and including 12.3(2)JK3 are not vulnerable.

Releases 12.3(8)JK1 and later are not vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3JL

Not Vulnerable

 

12.3JX

Not Vulnerable

 

12.3T

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3TPC

Releases up to and including 12.3(4)TPC11a are not vulnerable.

 

12.3VA

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.3XA

Releases prior to 12.3(2)XA7 are vulnerable, release 12.3(2)XA7 and later are not vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3XB

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

 

12.3XC

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3XD

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3XE

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3XF

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

 

12.3XG

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3XI

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

12.2(33)SB7

12.2(31)SB16

12.3XJ

Vulnerable; migrate to any release in 12.4XN

12.4(15)T10

12.3XK

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3XL

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3XQ

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3XR

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3XS

Not Vulnerable

 

12.3XU

Vulnerable; first fixed in 12.4T

Releases up to and including 12.3(8)XU1 are not vulnerable.

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.3XW

Vulnerable; migrate to any release in 12.4XR

12.4(15)XR7

12.4(22)XR

12.3XX

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3XY

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3XZ

Vulnerable; first fixed in 12.4

12.4(25b)

12.4(23b)

12.3YA

Not Vulnerable

 

12.3YD

Not Vulnerable

 

12.3YF

Vulnerable; migrate to any release in 12.4XR

12.4(15)XR7

12.4(22)XR

12.3YG

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.3YH

Not Vulnerable

 

12.3YI

Not Vulnerable

 

12.3YJ

Not Vulnerable

 

12.3YK

Releases prior to 12.3(11)YK3 are vulnerable, release 12.3(11)YK3 and later are not vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.3YM

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.3YQ

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.3YS

Vulnerable; first fixed in 12.4T

Releases up to and including 12.3(11)YS1 are not vulnerable.

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.3YT

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.3YU

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.3YX

Vulnerable; migrate to 12.4XR

12.4(15)XR7

12.4(22)XR

12.3YZ

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

 

12.3ZA

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

Affected 12.4-Based Releases

First Fixed Release

Recommended Release

12.4

12.4(25b)

12.4(23b)

12.4(25b)

12.4(23b)

12.4GC

Not Vulnerable

 

12.4JA

Not Vulnerable

 

12.4JDA

Not Vulnerable

 

12.4JDC

Not Vulnerable

 

12.4JDD

Not Vulnerable

 

12.4JK

Not Vulnerable

 

12.4JL

Not Vulnerable

 

12.4JMA

Not Vulnerable

 

12.4JMB

Not Vulnerable

 

12.4JX

Not Vulnerable

 

12.4MD

Not Vulnerable

 

12.4MDA

Not Vulnerable

 

12.4MR

Releases prior to 12.4(19)MR3 are vulnerable, release 12.4(19)MR3 and later are not vulnerable

 

12.4SW

Not Vulnerable

 

12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T2

12.4(24)T1

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4XA

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4XB

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4XC

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4XD

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4XE

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4XF

Not Vulnerable

 

12.4XG

Not Vulnerable

 

12.4XJ

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4XK

Not Vulnerable

 

12.4XL

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

 

12.4XM

Vulnerable; first fixed in 12.4T

Releases up to and including 12.4(15)XM are not vulnerable.

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4XN

Not Vulnerable

 

12.4XP

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

 

12.4XQ

Not Vulnerable

 

12.4XR

Not Vulnerable

 

12.4XT

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4XV

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

 

12.4XW

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4XY

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4XZ

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4YA

Vulnerable; first fixed in 12.4T

12.4(15)T10

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4YB

12.4(22)YB4

12.4(22)YB4

12.4YD

Not Vulnerable

 

12.4YE

Not Vulnerable

 

Note: No Cisco IOS-XE Software or Cisco IOS Software Modularity releases are affected by this vulnerability.


Workarounds

There are no workarounds to mitigate the vulnerability apart from disabling H.323 if the Cisco IOS device does not need to run H.323 for VoIP services. Affected devices that must run H.323 are vulnerable, and there are not any specific configurations that can be used to protect them. Applying access lists on interfaces that should not accept H.323 traffic and putting firewalls in strategic locations may greatly reduce exposure until an upgrade can be performed.

Cisco provides Solution Reference Network Design (SRND) guides to help design and deploy networking solutions, which can be found at http://www.cisco.com/go/srnd Voice Security best practices are covered in the Cisco Unified Communications SRND Based on Cisco Unified Communications Manager 6.x at http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/6x/security.html.

Below is an example of an access list to block H.323 management traffic from anywhere but a permitted network. In this example, the permitted network is 172.16.0.0/16.


!--- Permit access from any IP address in the 172.16.0.0/16 
!--- network to anywhere on port 1720.


access-list 101 permit tcp 172.16.0.0 0.0.255.255 any eq 1720


!--- Permit access from anywhere to a host in the 
!--- 172.16.0.0/26 network on port 1720.

 
access-list 101 permit tcp any 172.16.0.0 0.0.255.255 eq 1720


!--- Deny all traffic from port 1720.


access-list 101 deny tcp any eq 1720 any


!--- Deny all traffic to port 1720.


access-list 101 deny tcp any any eq 1720


!--- Permit all other traffic.


access-list 101 permit ip any any

Alternatively, you can use the call service stop forced command under the voice service voip mode, as shown in the following example:

voice service voip
 h323
  call service stop forced

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 Denial of Service Vulnerabilities in Cisco Unified Communications Manager and Cisco IOS Software", which is available at the following location: http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20090923-voice.

Obtaining Fixed Software

Cisco has released free software updates that address this vulnerability. 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/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 found during internal testing.

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-20090923-h323

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

2009-September-23

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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