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Category:   Device (Firewall)  >   Cisco Firewall Services Module Vendors:   Cisco
Cisco Firewall Services Module Can Be Crashed By Remote Users Sending SNMPv3 Messages
SecurityTracker Alert ID:  1008476
SecurityTracker URL:
CVE Reference:   CVE-2003-1002   (Links to External Site)
Updated:  Dec 18 2003
Original Entry Date:  Dec 15 2003
Impact:   Denial of service via network
Fix Available:  Yes  Vendor Confirmed:  Yes  Exploit Included:  Yes  
Version(s): 1.1.2 and earlier; FWSM for Cisco Catalyst 6500 Series and Cisco 7600 Series
Description:   A vulnerability was reported in the Cisco Firewall Services Module (FWSM) when SNMP support is enabled. A remote user can cause the firewall to crash.

It is reported that there is a flaw in the processing of SNMP messages. A remote user with an authorized IP address (or by spoofing that address) can send an SNMPv3 message to the target FWSM to cause the FWSM to crash and reboot. This can occur when the "snmp-server host <ip_addr>" command is configured on the FWSM. Cisco notes that the FWSM does not support SNMPv3.

Cisco has assigned Cisco Bug ID CSCeb88419 to this vulnerability.

Impact:   A remote user can cause the FWSM to crash and reboot.
Solution:   The vendor has released a fixed version (1.1.3 and later). For the procedure to upgrade to the fixed software version, see:

Vendor URL: (Links to External Site)
Cause:   Exception handling error

Message History:   None.

 Source Message Contents

Subject:  [Full-Disclosure] Cisco Security Advisory: Cisco FWSM Vulnerabilities

Hash: SHA1

              Cisco Security Advisory: Cisco FWSM Vulnerabilities

Revision 1.0

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



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



   This advisory documents two vulnerabilities for the Cisco Firewall
   Services Module for Cisco Catalyst 6500 Series and Cisco 7600 Series
   (FWSM). These vulnerabilities are documented as CSCeb16356 (HTTP Auth) and
   CSCeb88419 (SNMPv3).

   There are workarounds available to mitigate the effects of CSCeb88419
   (SNMPv3). No workaround is available for CSCeb16356 (HTTP Auth).

   This advisory will be posted at

Affected Products

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

     * CSCeb16356 (HTTP Auth)

       1.1.2 and earlier.

     * CSCeb88419 (SNMPv3)

       1.1.2 and earlier.

   The Cisco PIX firewall is also vulnerable to the SNMPv3 issue and is
   documented as No other
   Cisco products are currently known to be affected by these

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


     * CSCeb16356 (HTTP Auth)

       The Cisco FWSM may crash and reload due to a buffer overflow
       vulnerability while processing HTTP traffic requests for
       authentication using TACACS+ or RADIUS. This request is initiated when
       a user starting a connection via FTP, Telnet, or over the World Wide
       Web (HTTP) is prompted for their user name and password. If the user
       name and password are verified by the designated TACACS+ or RADIUS
       authentication server, the Cisco FWSM will allow further traffic
       between the authentication server and the connection to interact
       independently through the Cisco FWSM's "cut-through proxy" feature.

     * CSCeb88419 (SNMPv3)

       The Cisco FWSM crashes and reloads while processing a received SNMPv3
       message when snmp-server host <ip_addr> is configured on the Cisco
       FWSM. This happens even though the Cisco FWSM does not support SNMPv3.

   The Internetworking Terms and Cisco Systems Acronyms online guides can be
   found at

   These vulnerabilities are documented in the Cisco Bug Toolkit as Bug ID
   CSCeb16356 (HTTP Auth) and CSCeb88419 (SNMPv3). To access this tool, you
   must be a registered user and you must be logged in.


     * CSCeb16356 (HTTP Auth)

       This vulnerability can be exploited to initiate a Denial of Service
       attack on the Cisco FWSM.

     * CSCeb88419 (SNMPv3)

       This vulnerability can be exploited to initiate a Denial of Service
       attack on the Cisco FWSM.

Software Versions and Fixes

     * CSCeb16356 (HTTP Auth)

       1.1.3 and later.

     * CSCeb88419 (SNMPv3)

       1.1.3 and later.

   The procedure to upgrade to the fixed software version is detailed at

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, or as otherwise set
   forth at the Cisco Connection Online Software Center at

   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 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

   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:

   See for
   additional TAC contact information, including special localized telephone
   numbers and instructions and e-mail addresses for use in various

   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 "" or
   "" for software upgrades.


     * CSCeb16356 (HTTP Auth)

       No workaround. Please upgrade.

     * CSCeb88419 (SNMPv3)

       There are two workarounds available.

          * Restrict access to only allow trusted hosts on specific
            interfaces to poll the SNMP server on the FWSM.

            snmp-server host <if_name> <ip_addr> poll

          * Disable the SNMP server on the FWSM as follows:

            no snmp-server location

            no snmp-server contact

            snmp-server community public

            no snmp-server enable traps

            Note:  The Cisco FWSM 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

   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.

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

   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


   This advisory will be posted on Cisco's worldwide website at

   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.


     * (includes CERT/CC)







     * 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

   |            |                |Initial     |
   |Revision 1.0|2003-December-15|public      |
   |            |                |release.    |

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 This
   includes instructions for press inquiries regarding Cisco security
   notices. All Cisco security advisories are available at

   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.

Comment: PGP Signed by Sharad Ahlawat, Cisco Systems PSIRT


Full-Disclosure - We believe in it.


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