Cisco Security Advisory

Advisory ID: cisco-sa-20110223-asa

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20110223-asa

Revision 1.0

For Public Release 2011 February 23 16:00  UTC (GMT)

Summary

Cisco ASA 5500 Series Adaptive Security Appliances are affected by the following vulnerabilities:

• Transparent Firewall Packet Buffer Exhaustion Vulnerability
  
• Skinny Client Control Protocol (SCCP) Inspection Denial of Service Vulnerability
  
• Routing Information Protocol (RIP) Denial of Service Vulnerability
  
• Unauthorized File System Access Vulnerability
  

These vulnerabilities are independent; a release that is affected by one vulnerability is not necessarily affected by the others.

Cisco has released free software updates that address these vulnerabilities.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20110223-asa.

Note: The Cisco Firewall Services Module (FWSM) is affected by one of these vulnerabilities. A separate Cisco Security Advisory has been published to disclose the vulnerability that affects the Cisco FWSM. That advisory is available at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20110223-fwsm.

Affected Products

The Cisco ASA 5500 Series Adaptive Security Appliance is a modular platform that provides security and VPN services. It offers firewall, intrusion prevention system (IPS), anti-X, and virtual private network (VPN) services.

Cisco ASA 5500 Series Adaptive Security Appliances are affected by the following vulnerabilities:

Transparent Firewall Packet Buffer Exhaustion Vulnerability

A Cisco ASA 5500 Series Adaptive Security Appliance that is configured for transparent firewall mode is affected by a packet buffer exhaustion vulnerability that could cause an appliance to stop forwarding traffic once all packet buffers are depleted. The number of available packet buffers may decrease when a security appliance receives IPv6 traffic and is not configured for IPv6 operation. IPv6 transit traffic does not cause a problem.

Administrators can check packet buffer utilization by issuing the command show blocks and inspecting the output for the number of available 1,550-byte blocks. If the number of blocks is zero (indicated by 0 in the CNT column), then the security appliance may be experiencing this issue. For example:

ciscoasa# show blocks 
  SIZE    MAX    LOW    CNT
     0    400    360    400
     4    200    199    199
    80    400    358    400
   256   1412   1381   1412
  1550   6274      0      0
  ...

This vulnerability is documented in Cisco bug ID CSCtj04707 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2011-0393.

SCCP Inspection Denial of Service Vulnerability

Cisco ASA 5500 Series Adaptive Security Appliances are affected by a vulnerability that could cause the appliance to reload when it processes a malformed SCCP message. Appliances are only vulnerable if SCCP inspection is enabled.

Only transit traffic can trigger this vulnerability; traffic that is destined to the appliance will not trigger the vulnerability.

This vulnerability is documented in Cisco bug ID CSCtg69457 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2011-0394.

RIP Denial of Service Vulnerability

Cisco ASA 5500 Series Adaptive Security Appliances are affected by a vulnerability that could cause the appliance to reload when it processes valid RIP updates. Appliances are vulnerable only if both RIP and the Cisco Phone Proxy feature are enabled.

Note:  the affected configuration requires that a global media termination address is configured, which is the only possible configuration option in Cisco ASA Software versions 8.0 and 8.1. However, it is possible to tie a media termination address to an interface in Cisco ASA Software version 8.2 and later. This configuration is not vulnerable.

This vulnerability is documented in Cisco bug ID CSCtg66583 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2011-0395.

Unauthorized File System Access Vulnerability

Cisco ASA 5500 Series Adaptive Security Appliances are affected by a vulnerability that could allow unauthorized users to access a file system (flash:, disk0:, disk1:, etc. but not system:) when the security appliance is configured as a local CA server. No authentication is required. File systems could contain sensitive information, such as backup device configurations (which may contain passwords or shared secrets), Cisco ASA Software images, or digital certificates.

This vulnerability is documented in Cisco bug ID CSCtk12352 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2011-0396.

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.

Transparent Firewall Packet Buffer Exhaustion Vulnerability

Successful exploitation of this vulnerability could cause a decrease in the number of available packet buffers. Repeated exploitation could eventually deplete all available packet buffers, which may cause an appliance to stop forwarding traffic.

SCCP Inspection Denial of Service Vulnerability

Successful exploitation of this vulnerability could cause a reload of the affected device. Repeated exploitation may result in a sustained denial of service condition.

RIP Denial of Service Vulnerability

Successful exploitation of this vulnerability could cause a reload of the affected device. Repeated exploitation may result in a sustained denial of service condition.

Unauthorized File System Access Vulnerability

Successful exploitation of this vulnerability could allow unauthorized, unauthenticated users to retrieve files that are stored in an affected appliance's file system, which may contain sensitive information.

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.

Recommended Releases

The following table lists all recommended releases. These recommended releases contain the fixes for all vulnerabilities in this advisory. Cisco recommends upgrading to a release that is equal to or later than these recommended releases.

Software Download

Cisco ASA Software can be downloaded from the Software Center on Cisco.com by visiting http://www.cisco.com/cisco/software/navigator.html and navigating to Products > Security > Firewall > Firewall Appliances > Cisco ASA 5500 Series Adaptive Security Appliances > <your Cisco ASA model> > Adaptive Security Appliance (ASA) Software.

This Cisco Security Advisory describes multiple distinct vulnerabilities. These vulnerabilities and their respective workarounds are independent of each other.

Transparent Firewall Packet Buffer Exhaustion Vulnerability

There are no workarounds for this vulnerability.

SCCP Inspection Denial of Service Vulnerability

Administrators can mitigate this vulnerability by disabling SCCP inspection if it is not required. Administrators can disable SCCP inspection by issuing the no inspect skinny command in class configuration submode in the policy map configuration.

RIP Denial of Service Vulnerability

There are no workarounds for Cisco ASA Software version 8.0 and 8.1. On Cisco ASA Software version 8.2 and later, administrators can configure a non-global media termination address by specifying a termination address that will be tied to a specific interface. For example:

router rip
 ...

!

media-termination <instance name>
 address <IP address> interface <interface name>

!

<Rest of phone proxy feature configuration>

Unauthorized File System Access Vulnerability

There are no workarounds for this vulnerability.

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 Using Third-Party Support Organizations

Customers Without Service Contracts

The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerabilities described in this advisory.

The Transparent Firewall Packet Buffer Exhaustion Vulnerability, SCCP Inspection Denial of Service Vulnerability, and RIP Denial of Service Vulnerability were found during internal testing.

The Unauthorized File System Access Vulnerability was discovered during the resolution of customer support cases.

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.

This advisory is posted on Cisco's worldwide website at :

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20110223-asa

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.

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.