Summary

• Cisco Application Velocity System's (AVS) default configuration allows transparent relay of TCP connections to any reachable destination TCP port if the receiving TCP service can process requests embedded in a HTTP POST method message. This issue does not require a software upgrade and can be mitigated by a configuration command for all affected customers.

  Fixed versions of the AVS software have been modified to provide a more secure default configuration.

  Cisco has made free software available to address this vulnerability for affected customers installing new AVS Devices. The available workaround must be manually configured to mitigate the impact of this vulnerability for existing AVS devices even if upgrading to a fixed version of software.

  This advisory is posted at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20060510-avs

Affected Products

• This section provides details on affected products.

  Vulnerable Products

  AVS 3110 and 3120 Application Velocity Systems running all software versions prior to 5.0.1 are affected.

  • AVS 3110 4.0 and 5.0
    

  • AVS 3120 5.0.0
    

  as well as all prior versions for both devices.

  Products Confirmed Not Vulnerable

  The AVS 3180 Management Station is not affected by this vulnerability.

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

Details

• The Cisco AVS 3100 series Application Velocity System is an enterprise appliance for improving application performance. Using the Application Velocity System, web applications deployed across the WAN can offer response times typically expected from LAN environments.

  By default, the AVS is normally deployed as a transparent proxy. The transparent proxy feature may be exploited to open a TCP connection to any reachable destination TCP port and hide the true IP source address of the connection TCP port, if the receiving service can process requests embedded in a HTTP POST method message.

  This issue has been resolved by changing the default behavior such that connections are limited based on the destination port numbers and connections to TCP ports other than 80 and 443 are denied.

  This issue is documented by the following Cisco bug ID:

  • CSCsd32143 (registered customers only)
    

  Note: The available workaround must be manually configured to mitigate the impact of this vulnerability for existing AVS devices even if upgrading to a fixed version of software.

Workarounds

• For existing AVS devices, this issue must be resolved by a configuration command which blocks the use of redirected proxy requests for any TCP ports other than TCP/80 and TCP/443. To avoid writing over an existing configuration, this command must be manually applied even if software is upgraded to a fixed version. The configuration commands below should be added to the fgn.conf configuration file using the AVS Management Console.

  <DestinationMapping>
  Name default:80 -> default:80
  Name default:443 -> default:443
  Name default -> localhost:9
  </DestinationMapping>

  With this Destination map, only TCP connections to ports 80 and 443 will be forwarded. The AVS will reset connections destined to any other ports. If HTTP connections must be completed to other TCP ports, they must also be added to the configuration element using the same syntax as shown above. If destinations are already set in the configuration element, only the

  Name default -> localhost:9
  

  configuration line needs to be added as the last line in the Destination map. Adding this line before other lines in the Destination map may block legitimate traffic. After updating the Destination map element, the configuration changes must be published.

  For information on using the AVS Management Console refer to: http://www.cisco.com/en/US/products/ps6492/products_user_guide_chapter09186a008059be02.html

  For information about the fgn.conf file refer to: http://www.cisco.com/en/US/products/ps6492/products_user_guide_chapter09186a008059bddb.html#wp1045951

  For information about Destination Mapping refer to: http://www.cisco.com/en/US/products/ps6492/products_user_guide_chapter09186a008059bddb.html#wp1045807

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.

  This issue is fixed for new installations in AVS version 5.0.1 for both the AVS 3110 and AVS 3120.

  Software for AVS 3110 is available at http://www.cisco.com/pcgi-bin/tablebuild.pl/AVS3110-5.0.1

  Software for AVS 3120 is available at http://www.cisco.com/pcgi-bin/tablebuild.pl/AVS3120-5.0.1

  Note:  The available workaround must be manually configured to mitigate the impact of this vulnerability for existing AVS devices even if upgrading to a fixed version of software.

Exploitation and Public Announcements

• The Cisco PSIRT is aware of an instance in which the AVS has been used to transmit unsolicited commercial e-mail and hide the true source of the message.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20060510-avs

Revision History

• Revision 1.0

  2006-May-10

  Initial public release

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