Products & Services

The following paragraphs describe the affected Cisco ASA and Cisco PIX software versions:

Vulnerable Products

Products Confirmed Not Vulnerable

The following sections provide details to help determine if a device may be affected by any of the vulnerabilities.

Erroneous SIP Processing Vulnerabilities

Cisco PIX and Cisco ASA devices configured for SIP inspection are vulnerable to multiple processing errors that may result in denial of service attacks. All Cisco PIX and Cisco ASA software releases may be vulnerable to these SIP processing vulnerabilities. A successful attack may result in a reload of the device.

SIP inspection is enabled with the inspect sip command.

To determine whether the Cisco PIX or Cisco ASA security appliance is configured to support inspection of sip packets, log in to the device and issue the CLI command show service-policy | include sip. If the output contains the text Inspect: sip and some statistics, then the device has a vulnerable configuration. The following example shows a vulnerable Cisco ASA Security Appliance:

asa#show service-policy | include sip
      Inspect: sip, packet 0, drop 0, reset-drop 0

asa#

These vulnerability is documented in the following Cisco Bug IDs and has been assigned Common Vulnerabilities and Exposures (CVE) identifier CVE-2008-2732.

• CSCsq07867 (registered customers only)
  
• CSCsq57091 (registered customers only)
  
• CSCsk60581 (registered customers only)
  
• CSCsq39315 (registered customers only)
  

IPSec Client Authentication Processing Vulnerability

Cisco PIX and Cisco ASA devices configured to terminate client based VPN connections are vulnerable to a crafted authentication processing vulnerability if they are running software versions 7.2, 8.0, or 8.1. Devices that run software versions 7.0 or 7.1 are not affected by this vulnerability.

A successful attack may result in a reload of the device.

Remote access VPN connections will have Internet Security Association and Key Management Protocol (ISAKMP) enabled on an interface with the crypto command, such as: crypto isakmp enable outside.

This vulnerability is documented in Cisco Bug ID CSCso69942 (registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) identifier CVE-2008-2733.

SSL VPN Memory Leak Vulnerability and URI Processing Error Vulnerability in SSL VPNs

A crafted SSL or HTTP packet may cause a denial of service condition on a Cisco ASA device that is configured to terminate clientless VPN connections. A successful attack may result in a reload of the device.

Cisco ASA devices that run versions 7.2, 8.0, or 8.1 with clientless SSL VPNs enabled may be affected by this vulnerability. Devices that run software versions 7.0 and 7.1 are not affected by this vulnerability.

Clientless VPN, SSL VPN Client, and AnyConnect connections are enabled via the webvpn command. For example, the following configuration shows a Cisco ASA with Clientless VPNs configured and enabled. In this case the ASA will listen for VPN connections on the default port, TCP port 443:

http server enable                                                              
!
webvpn
 enable outside

Note that with this particular configuration, the device is vulnerable to attacks coming from the outside interface due to the enable outside command within the webvpn group configuration.

These vulnerabilities are documented in Cisco Bug ID CSCso66472 (registered customers only) and CSCsq19369 (registered customers only) . They have been assigned Common Vulnerabilities and Exposures (CVE) identifiers CVE-2008-2734 and CVE-2008-2735.

Potential Information Disclosure in Clientless VPNs

On Cisco ASA devices configured to terminate clientless VPN connections, an attacker may be able to discover potentially sensitive information such as usernames and passwords. This attack requires an attacker to convince a user to visit a rogue web server, reply to an e-mail, or interact with a service to successfully exploit the vulnerability.

Cisco ASA devices running software versions 8.0 or 8.1 with clientless VPNs enabled may be affected by this vulnerability. Cisco ASA devices running that run software versions 7.0, 7.1, or 7.2 are not vulnerable to this vulnerability.

Clientless SSL VPN connections are enabled via the webvpn command. For example, the following configuration shows a Cisco ASA device with Clientless VPNs configured and enabled. In this case the Cisco ASA device will listen for VPN connections on the default port, TCP port 443:

http server enable                                                              
!
webvpn
 enable outside

Note that with this particular configuration, the device is vulnerable to attacks coming from the outside interface due to the enable outside command within the webvpn group configuration.

This vulnerability is documented in Cisco Bug ID CSCsq45636 (registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) identifier CVE-2008-2736.

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 calculated 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.

Erroneous SIP Processing Vulnerabilities

IPSec Client Authentication Processing Vulnerability

SSL VPN Memory Leak Vulnerability

URI Processing Error Vulnerability in SSL VPNs

Potential Information Disclosure in Clientless VPNs

Successful exploitation of the Erroneous SIP Processing Vulnerabilities, IPSec Client Authentication Processing Vulnerability, SSL VPN Memory Leak Vulnerability, or URI Processing Error Vulnerability in SSL VPNs may result in the device reloading. This can be repeatedly exploited and may lead to a denial of service attack.

The Potential Information Disclosure in Clientless SSL VPNs vulnerability may allow an attacker to obtain user and group credentials if the user interacts with a rogue system or document.

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.

The following list contains the first fixed software release of each vulnerability:

The "Recommended Release" row indicates the releases which have fixes for all the published vulnerabilities at the time of this Advisory. A device running a version of the given release in a specific row (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 Release" row of the table.

Fixed Cisco PIX software can be downloaded from: http://www.cisco.com/pcgi-bin/tablebuild.pl/pix-interim?psrtdcat20e2

Fixed Cisco ASA software can be downloaded from: http://www.cisco.com/pcgi-bin/tablebuild.pl/asa-interim?psrtdcat20e2

The following workarounds may help some customers mitigate these vulnerabilities.

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: http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20080903-asa

Erroneous SIP Processing Vulnerabilities

SIP inspection should be disabled if it is not needed and temporarily disabling the feature will mitigate the SIP processing vulnerabilities. SIP inspection can be disabled with the command no inspect sip.

IPSec Authentication Processing Vulnerability

Use strong group credentials for remote access VPN connections and do not give out the group credentials to end users.

SSL VPN Memory Leak Vulnerability and URI Processing Error Vulnerability in SSL VPNs

IPSec clients are not vulnerable to this issue and may be used in conjunction with strong group credentials until the device can be upgraded.

Potential Information Disclosure in Clientless SSL VPNs

Client based VPN connections are not vulnerable to the information disclosure vulnerability. If you are running 8.0(3)15, 8.0(3)16, 8.1(1)4, or 8.1(1)5, you may safely use client based VPN connections as an alternative to clientless VPNs.

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 vulnerability described in this advisory.

These vulnerabilities were reported to Cisco by customers that experienced these issues during normal operation of their equipment and through internal testing efforts.

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-20080903-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/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.