Cisco Security Advisory: Cisco PIX Vulnerabilities

Document ID: 47284

Revision 1.2

Last Updated 2004 January 26 at 1600 GMT

For Public Release 2003 December 15 at 1600 UTC (GMT)

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Contents

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

Summary

This advisory documents two vulnerabilities for the Cisco PIX firewall. These vulnerabilities are documented as CSCeb20276 (SNMPv3) and CSCec20244 (VPNC).

There are workarounds available to mitigate the effects of CSCeb20276 (SNMPv3). No workaround is available for CSCec20244 (VPNC).

This advisory will be posted at http://www.cisco.com/warp/public/707/cisco-sa-20031215-pix.shtml.

Affected Products

All Cisco PIX firewall devices running the affected Cisco PIX firewall software, as documented below, are affected by these vulnerabilities.

• CSCeb20276 (SNMPv3)
  6.3.1, 6.2.2 and earlier, 6.1.4 and earlier. 5.x.x and earlier.
  
• CSCec20244 (VPNC)
  6.2 (2.119) to 6.2.3, both inclusive.
  6.3.x and 6.2.1 to 6.2 (2.118) are not affected.
  

The Firewall Service Module (FWSM) is also vulnerable to the SNMPv3 issue and is documented as http://www.cisco.com/warp/public/707/cisco-sa-20031215-fwsm.shtml. No other Cisco products are currently known to be affected by these vulnerabilities.

To determine your software revision, type show version at the command line prompt.

Details

• CSCeb20276 (SNMPv3)
  The Cisco PIX firewall crashes and reloads while processing a received SNMPv3 message when snmp-server host <if_name> <ip_addr> or snmp-server host <if_name> <ip_addr> poll is configured on the Cisco PIX firewall. This happens even though the Cisco PIX firewall does not support SNMPv3.
  A Cisco PIX firewall configured to only generate and send traps using the snmp-server host <if_name> <ip_addr> trap command is not vulnerable.
  
• CSCec20244 (VPNC)
  Under certain conditions an established VPNC IPSec tunnel connection is dropped if another IPSec client attempts to initiate an IKE Phase I negotiation to the outside interface of the VPN Client configured Cisco PIX firewall.
  Only a Cisco PIX firewall configured as a VPN Client is vulnerable to this vulnerability. A device reload of the VPN Client configured PIX is required to recover from this unstable state. No action is required on the headend VPN concentrator.
  A VPNC, also referred to as Easy VPN or ezVPN, connection is created when the Cisco PIX firewall is used as a VPN client to connect to a VPN server. An IKE Phase I negotiation is a step in the establishment of an IPSec session.
  CSCec20244 resolved this issue for the 6.2 (3.100) and later software releases.
  

The Internetworking Terms and Cisco Systems Acronyms online guides can be found at http://www.cisco.com/univercd/cc/td/doc/cisintwk/.

These vulnerabilities are documented in the Cisco Bug Toolkit as Bug ID CSCeb20276 (SNMPv3) and CSCec20244 (VPNC). To access this tool, you must be a registered user and you must be logged in.

Impact

• CSCeb20276 (SNMPv3)
  This vulnerability can be exploited to initiate a Denial of Service attack on the Cisco PIX firewall.
  
• CSCec20244 (VPNC)
  This vulnerability can be exploited to initiate a Denial of Service attack on sessions established between a Cisco PIX configured as a VPN Client and a VPN server.
  

Software Versions and Fixes

• CSCeb20276 (SNMPv3)
  6.3.2 and later, 6.2.3 and later, 6.1.5 and later.
  
• CSCec20244 (VPNC)
  6.3.1 and later, 6.2(3.100) and later.
  

The procedure to upgrade to the fixed software version is detailed at http://www.cisco.com/univercd/cc/td/doc/product/iaabu/pix/pix_sw/index.htm.

Obtaining Fixed Software

Cisco is offering free software upgrades to address these vulnerabilities for all affected customers.

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/public/sw-license-agreement.html, or as otherwise set forth at the Cisco Connection Online Software Center at http://www.cisco.com/public/sw-center/sw-usingswc.shtml.

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/tacpage/sw-center/ciscosecure/pix.shtml. To access the software download URL, you must be a registered user and you must be logged in.

Customers whose Cisco products are provided or maintained through prior or existing agreement with third-party support organizations such as Cisco Partners, authorized resellers, or service providers should contact that support organization for assistance with obtaining the software upgrade(s).

Customers who purchase direct from Cisco but who do not hold a Cisco service contract and customers who purchase through third-party vendors but are unsuccessful at obtaining fixed software through their point of sale should get their upgrades by contacting the Cisco Technical Assistance Center (TAC) using the contact information listed below. In these cases, customers are entitled to obtain an upgrade to a later version of the same release or as indicated by the applicable corrected software version in the Software Versions and Fixes section (noted above).

Cisco 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
  

See http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for additional TAC contact information, including special localized telephone numbers and instructions and e-mail addresses for use in various languages.

Please have your product serial number available and give the URL of this notice as evidence of your entitlement to a upgrade. Upgrades for non-contract customers must be requested through the TAC.

Please do not contact either "psirt@cisco.com" or "security-alert@cisco.com" for software upgrades.

Workarounds

• CSCeb20276 (SNMPv3)
  There are two workarounds available.
  
  • If SNMP polling to the PIX is required on a vulnerable image, one may choose to restrict the polling access to the SNMP server to trusted interfaces and trusted hosts by using this command:
    snmp-server host <if_name> <ip_addr> poll
    

    Note:  Both Poll and Trap are enabled if one does not specifically use the poll or trap keyword in the command above. The above command cannot prevent a source IP spoofed SNMP request message from exploiting this vulnerability. Prior to software version 6.0, one cannot selectively enable poll and trap functionality because there are no Poll and Trap keywords in the snmp-server host <if_name> <ip addr> command.

  • Disable the SNMP server on the Cisco PIX firewall as follows:
    clear snmp-server
    no snmp-server location
    no snmp-server contact
    snmp-server community public
    no snmp-server enable traps
    

    Note:  The Cisco PIX firewall does not allow one to remove the community string altogether. It will always be either public or a user configured string. show snmp will still show snmp-server community public, but this does not mean SNMP is enabled.

  More details at http://www.cisco.com/univercd/cc/td/doc/product/iaabu/pix/pix_62/cmdref/s.htm#1026423.
  
• CSCec20244 (VPNC)
  No workaround. Please upgrade.
  

The Cisco PSIRT recommends that affected users upgrade to a fixed software version of code.

Exploitation and Public Announcements

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

CSCeb20276 (SNMPv3) was reported to the PSIRT by Rasto Rickardt.

Status of This Notice: Final

This is a final advisory. Although Cisco cannot guarantee the accuracy of all statements in this advisory, all of the facts have been checked to the best of our ability. Cisco does not anticipate issuing updated versions of this advisory unless there is some material change in the facts. Should there be a significant change in the facts, Cisco may update this advisory.

A stand-alone copy or paraphrase of the text of this security advisory 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 will be posted on Cisco's worldwide website at http://www.cisco.com/warp/public/707/cisco-sa-20031215-pix.shtml.

In addition to worldwide web posting, a text version of this notice is clear-signed with the Cisco PSIRT PGP key having the fingerprint 8C82 5207 0CA9 ED40 1DD2 EE2A 7B31 A8CF 32B6 B590, and is posted to the following e-mail and Usenet news recipients.

• cust-security-announce@cisco.com
  
• first-teams@first.org (includes CERT/CC)
  
• bugtraq@securityfocus.com
  
• vulnwatch@vulnwatch.org
  
• cisco@spot.colorado.edu
  
• cisco-nsp@puck.nether.net
  
• full-disclosure@lists.netsys.com
  
• comp.dcom.sys.cisco@newsgate.cisco.com
  
• Various internal Cisco mailing lists
  

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

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.

This advisory is copyright 2003 by Cisco Systems, Inc. This advisory may be redistributed freely after the release date given at the top of the text, provided that redistributed copies are complete and unmodified, including all date and version information.

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