Cisco Security Advisory: Cisco IOS Software H.323 Denial of Service Vulnerability

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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)

Summary
Affected Products
Details
Vulnerability Scoring Details
Impact
Software Versions and Fixes
Workarounds
Obtaining Fixed Software
Exploitation and Public Announcements
Status of This Notice: Final
Distribution
Revision History
Cisco Security Procedures

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/en/US/products/products_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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Cisco Security Advisory

Cisco IOS Software H.323 Denial of Service Vulnerability

Advisory ID: cisco-sa-20090923-h323

Revision 1.1

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

Contents

writePM('affected')Affected Products

writePM('vps') Vulnerable Products

writePM('nonvulnerable')Products Confirmed Not Vulnerable

writePM('details')Details

writePM('vulnerability')Vulnerability Scoring Details

writePM('impact')Impact

writePM('software')Software Versions and Fixes

writePM('workarounds')Workarounds

writePM('fixes')Obtaining Fixed Software

writePM('CustomerswithServiceContracts')Customers with Service Contracts

writePM('CustomerSupportOrganizationsConcepts')Customers Using Third-Party Support Organizations

writePM('CustomerswithoutServiceContracts')Customers Without Service Contracts

writePM('exploitation')Exploitation and Public Announcements

writePM('status')Status of This Notice: Final

writePM('distribution')Distribution

writePM('revision')Revision History

writePM('secpro')Cisco Security Procedures

Related Links

Tools

Products & Services

Solutions

Affected Products

Vulnerable Products

Products Confirmed Not Vulnerable

Details

Vulnerability Scoring Details

Impact

Software Versions and Fixes

Workarounds

Obtaining Fixed Software

Customers with Service Contracts

Customers Using Third-Party Support Organizations

Customers Without Service Contracts

Exploitation and Public Announcements

Status of This Notice: Final

Distribution

Revision History

Cisco Security Procedures