__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Cisco 11500 Content Services Switch SSL Malformed Client Certificate Vulnerability [Cisco Security Advisory Document ID: 67919] October 20, 2005 17:00 GMT Number Q-029 ______________________________________________________________________________ PROBLEM: Cisco CSS 11500 Series Content Services Switchs (CSS) configured with Secure Socket Layer (SSL) termination services are vulnerable to a Denial of Service (DoS) attack when processing malformed client certificates. PLATFORM: Cisco CSS 11500 Series Content Services Switches running the following versions of the Cisco WebNS operating system: 7.1 7.2 7.3 7.4 7.5 DAMAGE: Denial of Service attack. SOLUTION: Upgrade to the appropriate version. ______________________________________________________________________________ VULNERABILITY The risk is LOW. Denial of Service attack. ASSESSMENT: ______________________________________________________________________________ LINKS: CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/q-029.shtml ORIGINAL BULLETIN: Cisco Security Advisory Document ID: 67919 http://www.cisco.com/en/US/products/products_security_ advisory09186a008054bc9b.shtml ______________________________________________________________________________ [***** Start Cisco Security Advisory Document ID: 67919 *****] Cisco 11500 Content Services Switch SSL Malformed Client Certificate Vulnerability Document ID: 67919 Revision 1.1 Last Updated 2005 October 19 2200 UTC (GMT) For Public Release 2005 October 19 1600 UTC (GMT) -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- 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 Cisco CSS 11500 Series Content Services Switches (CSS) configured with Secure Socket Layer (SSL) termination services are vulnerable to a Denial of Service (DoS) attack when processing malformed client certificates. Cisco has made free software available to address this vulnerability. There are workarounds available to mitigate the effects of the vulnerability. This advisory is posted at http://www.cisco.com/warp/public/707/cisco-sa-20051019 -css.shtml. Affected Products Vulnerable Products Cisco CSS 11500 Series Content Services Switches running the following versions of the Cisco WebNS operating system: * 7.1 * 7.2 * 7.3 * 7.4 * 7.5 The version of Cisco WebNS running on a CSS can be determined by running the following command: # show version Products Confirmed Not Vulnerable Cisco CSS 11000 Series Content Services Switches No other Cisco products are currently known to be affected by these vulnerabilities. Details The Cisco CSS 11500 Content Service Switch is load balancing device designed to provide robust, scalable network services (Layer 4-7) for data centers. The Cisco CSS 11500 performs an analysis of protocol headers and directs requests to an appropriate resource based on configurable policies. With integrated SSL modules, a Cisco CSS 11500 can simplify the management of digital cerfiticates and provide SSL acceleration services to optimize performance. A Cisco CSS 11500 may reload due to a memory corruption issue when presented with a malformed digital client certificate during the negotiation of a SSL session. This condition is present even if the CSS did not request a client certificate during SSL session negotiations. This vulnerability is only present if a CSS is configured to support SSL termination services. SSL termination services are not configured by default. Users can determine if SSL termination services are configured on a CSS by performing the following steps. * View the current running configuration: # show running-config In the Services section of the configuration, users can find enabled SSL termination services. An example of an enabled SSL termination service called ssl-serv1 will look similar to the following. The type command with the option ssl-accel or ssl-accel-backend indicates that the service is associated with a SSL module, and the active command signifies that a SSL termination service is enabled. service ssl-serv1 type ssl-accel slot 3 keepalive type none add ssl-proxy-list ssl list1 active The vulnerability is documented in the following Cisco Bug ID: * CSCee64771 ( registered customers only) -- CSS running SSL may crash with malformed client certificates Impact Successful exploitation of the vulnerability may result in the immediate reload of the device. Repeated exploitation could result in a sustained DoS attack. Software Versions and Fixes When considering software upgrades, consult http://www.cisco.com/en/US/products/products_security_advisories_listing.html 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") for assistance. Train Fixed Releases 7.3 7.30.4.02 and later 7.4 7.40.2.02 and later 7.5 7.50.1.03 and later Customers running Cisco WebNS 7.10 and 7.20 are encouraged to upgrade CSS platforms to a fixed version of Cisco WebNS 7.30 or greater. Fixed software may be obtained by registered users at http://www.cisco.com/pcgi-bin/tablebuild.pl/ css11500-maint?psrtdcat20e2. Obtaining Fixed Software Customers with Service Contracts 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. Customers using Third-party Support Organizations 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 the upgrade, which should be free of charge. Customers without Service Contracts 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). 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 Have your product serial number available and give the URL of this notice as evidence of your entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC. Do not contact either "psirt@cisco.com" or "security-alert@cisco.com" for software upgrades. Refer to 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. 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 Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml. Workarounds The effectiveness of any workaround is dependent on specific customer situations such as product mix, network topology, traffic behavior, and organizational mission. Due to the variety of affected products and releases, customers should consult with their service provider or support organization to ensure any applied workaround is the most appropriate for use in the intended network before it is deployed. If upgrading to a fixed version of Cisco WebNS software is not possible, the following workarounds are available. *Disable SSL termination for network services if not needed. In service configuration mode, a user can disable a SSL service using the following commands. ssl-serv1 is the name of a user defined SSL service. (config)# no service ssl-serv1 Delete service , [y/n]:y Documentation for configuring SSL services on a CSS running Cisco WebNS 7.40 can be found at http://www.cisco.com/en/US/products/hw/contnetw/ps792/products_ configuration_guide_book09186a008027ab4e.html. Documentation for configuring SSL services on a CSS running Cisco WebNS 7.50 can be found at http://www.cisco.com/en/US/products/hw/contnetw/ps792/products_ configuration_guide_book09186a0080405453.html. *Use Access Control Lists (ACL) on a CSS or network device in front of a CSS to restrict access to SSL terminated services to trusted networks. Documentation for configuring an ACL on a CSS running Cisco WebNS 7.40 can be found at http://www.cisco.com/en/US/products/hw/contnetw/ps792/products_ configuration_guide_chapter09186a008029b1db.html#wp1133930. Documentation for configuring an ACL on a CSS running Cisco WebNS 7.50 can be found at http://www.cisco.com/en/US/products/hw/contnetw/ps792/products_ configuration_guide_chapter09186a008040aeb9.html#wp1133930. Exploitation and Public Announcements The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory. Status of This Notice: FINAL THIS ADVISORY IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTY OF MERCHANTABILITY. YOUR USE OF THE INFORMATION ON THE ADVISORY OR MATERIALS LINKED FROM THE ADVISORY IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS NOTICE AT ANY TIME. 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 is posted on Cisco's worldwide website at http://www.cisco.com/warp/public /707/cisco-sa-20051019-css.shtml. 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-teams@first.org (includes CERT/CC) * 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. Revision History Revision 1.1 2005-October-19 Added direct links to fixed software in Software Versions and Fixes table. Revision 1.0 2005-October-19 Initial 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 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. [***** End Cisco Security Advisory Document ID: 67919 *****] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Cisco for the information contained in this bulletin. _______________________________________________________________________________ CIAC, the Computer Incident Advisory Capability, is the computer security incident response team for the U.S. Department of Energy (DOE) and the emergency backup response team for the National Institutes of Health (NIH). CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. CIAC services are available to DOE, DOE contractors, and the NIH. CIAC can be contacted at: Voice: +1 925-422-8193 (7x24) FAX: +1 925-423-8002 STU-III: +1 925-423-2604 E-mail: ciac@ciac.org Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://www.ciac.org/ Anonymous FTP: ftp.ciac.org PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing communities receive CIAC bulletins. If you are not part of these communities, please contact your agency's response team to report incidents. Your agency's team will coordinate with CIAC. The Forum of Incident Response and Security Teams (FIRST) is a world-wide organization. A list of FIRST member organizations and their constituencies can be obtained via WWW at http://www.first.org/. This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. 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