Summary

• Cisco Unified Communications Manager, formerly Cisco CallManager, contains a denial of service (DoS) vulnerability in the Certificate Authority Proxy Function (CAPF) service. Exploitation of this vulnerability could cause an interruption in voice services. The CAPF service is disabled by default.

  Cisco has released software updates that address this vulnerability. Workarounds available that mitigate this vulnerability are available.

  This advisory is posted at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20090121-cucmcapf.

Affected Products

• Vulnerable Products

  These products are vulnerable:

  • Cisco Unified Communications Manager 5.x versions prior to 5.1(3e)
    
  • Cisco Unified Communications Manager 6.x versions prior to 6.1(3)
    

  Administrators of systems that are running Cisco Unified Communications Manager versions 5.x and 6.x can determine the software version by viewing the main page of the Cisco Unified Communications Manager Administration interface. The software version can also be determined by running the command show version active by way of the command line interface (CLI).

  Products Confirmed Not Vulnerable

  Cisco Unified Communications Manager version 4.x and Cisco Unified Communications Manager Express are not affected by this vulnerability. No other Cisco products are currently known to be affected by this vulnerability.

  Note: Cisco Unified Communications Manager 7.0(1) shipped with the software fix for this vulnerability and is not affected.

Details

• The CAPF service of Cisco Unified Communications Manager versions 5.x and 6.x contain a vulnerability when handling malformed input that may result in a DoS condition. The CAPF service is disabled by default; however, if it is enabled, the CAPF service listens by default on TCP port 3804 and the listening port is configurable by the user. There is a workaround for this vulnerability. This vulnerability is fixed in Cisco Unified Communications Manager versions 5.1(3e) and 6.1(3). This vulnerability is documented in Cisco Bug ID CSCsq32032 and has been assigned Common Vulnerabilities and Exposures (CVE) identifier CVE-2009-0057.

Workarounds

• To mitigate against this vulnerability, system administrators can disable the CAPF service if it is not necessary for business operations. Access to the CAPF service is only required if Cisco Unified Communications Manager systems and IP phone devices are configured to use certificates for a secure deployment. If phones are not configured to use certificates, then the CAPF service can be disabled. The CAPF service is controlled by the Cisco Certificate Authority Proxy Function menu selection.

  It is possible to mitigate the CAPF vulnerability by implementing filtering on screening devices if the CAPF service is required. If the CAPF service is enabled, allow access to TCP port 3804 only from networks that contain IP phone devices that require the CAPF service. The CAPF port is user configurable, and if modified, filtering on screening devices should be based on the TCP port that is used.

  For Cisco Unified Communications Manager 5.x and 6.x systems, please consult the following documentation for details on how to disable Cisco Unified Communications Manager services:

  http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/service/5_0_1/ccmsrva/sasrvact.html#wp1048220

  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:

  https://sec.cloudapps.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20090121-cucmcapf

Fixed Software

• 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.

  Cisco Unified Communications Manager version 5.1(3e) contains the fix for this vulnerability and can be downloaded here:

  https://sec.cloudapps.cisco.com/support/downloads/go/ReleaseType.x?optPlat=null&isPlatform=Y&mdfid=280735907&sftType=Unified%20Communications%20Manager%20Updates&treeName=Voice%20and%20Unified%20Communications&modelName=Cisco%20Unified%20Communications%20Manager%20Version%205.1&mdfLevel=Software%20Version/Option&treeMdfId=278875240&modifmdfid=null&imname=null&hybrid=Y&imst=N ( registered customers only)

  Cisco Unified Communications Manager version 6.1(3) contains the fix for this vulnerability can downloaded here:

  https://sec.cloudapps.cisco.com/support/downloads/go/PlatformList.x?sftType=Unified%20Communications%20Manager%20Updates&mdfid=281023410&treeName=Voice%20and%20Unified%20Communications&mdfLevel=Software%20Version/Option&url=null&modelName=Cisco%20Unified%20Communications%20Manager%20Version%206.1&isPlatform=N&treeMdfId=278875240&modifmdfid=null&imname=null&hybrid=Y&imst=N ( registered customers only)

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 reported to Cisco by VoIPshield.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20090121-cucmcapf

Revision History

• Revision 1.0

  2009-January-21

  Initial public release

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