__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Cisco Unified Communications Manager Denial of Service Vulnerabilities [Cisco Security Advisory Document ID: 98833] October 18, 2007 13:00 GMT Number S-017 ______________________________________________________________________________ PROBLEM: Cisco Unified Communications Manager (CUCM), formerly CallManager, contains two denial of service (DoS) vulnerabilities. PLATFORM: Cisco Unified CallManager 5.0 versions Cisco Communications Manager 5.1 versions prior to 5.1(2) DAMAGE: May result in a DoS condition and also provide the ability to execute arbitrary code. SOLUTION: Upgrade to the appropriate version. ______________________________________________________________________________ VULNERABILITY The risk is MEDIUM. May result in a DoS condition and also ASSESSMENT: provide the ability to execute arbitrary code. ______________________________________________________________________________ LINKS: CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/s-017.shtml ORIGINAL BULLETIN: http://www.cisco.com/warp/public/707/cisco-sa-20071017- cucm.shtml#@ID ______________________________________________________________________________ [***** Start Cisco Security Advisory Document ID: 98833 *****] Cisco Security Advisory: Cisco Unified Communications Manager Denial of Service Vulnerabilities Document ID: 98833 Advisory ID: cisco-sa-20071017-cucm http://www.cisco.com/warp/public/707/cisco-sa-20071017-cucm.shtml Revision 1.0 For Public Release 2007 October 17 1600 UTC (GMT) -------------------------------------------------------------------------------- Please provide your feedback on this document. -------------------------------------------------------------------------------- Contents Summary Affected Products Details Vulnerability Scoring Details Impact Software Versions and Fixes Workarounds Obtaining Fixed Software Customers with Service Contracts Customers using Third Party Support Organizations Customers without Service Contracts Exploitation and Public Announcements Status of this Notice: FINAL Distribution Revision History Cisco Security Procedures -------------------------------------------------------------------------------- Summary Cisco Unified Communications Manager (CUCM), formerly CallManager, contains two denial of service (DoS) vulnerabilities. Large volumes of UDP Session Initiation Protocol (SIP) INVITE messages may cause a resource exhaustion condition on CUCM systems resulting in a kernel panic. The CUCM Trivial File Transfer Protocol (TFTP) service contains a buffer overflow vulnerability that may result in a denial of service condition or allow a remote, unauthenticated user to execute arbitrary code. There are no workarounds for these vulnerabilities. Cisco has made free software available to address these vulnerabilities for affected customers. This advisory is posted at http://www.cisco.com/warp/public/707/cisco-sa-20071017-cucm.shtml. [Expand all sections] [Collapse all sections] Affected Products Note: Cisco Unified CallManager versions 4.2, 4.3, 5.1 and 6.0 have been renamed Cisco Unified Communications Manager. CUCM versions 3.3, 4.0, 4.1 and 5.0 retain the Cisco Unified CallManager name. Vulnerable Products All Cisco Unified CallManager 5.0 versions and Communications Manager 5.1 versions prior to 5.1(2) are affected by both vulnerabilities. Cisco Unified Communications Manager version 5.1(2) is affected by the TFTP service overflow vulnerability. Note: Cisco Unified Communications Manager version 6.0(1) shipped containing the fixes for these vulnerabilities. Administrators of systems that are running CUCM versions 5.x and 6.x can determine the software version by viewing the main page of the CUCM Administration interface. The software version can also be determined by running the command show version active via the command line interface (CLI). Products Confirmed Not Vulnerable Cisco Unified CallManager versions 3.x, 4.0 and 4.1, Communications Manager 4.2 and 4.3, and Cisco CallManager Express are not affected by these vulnerabilities. No other Cisco products are currently known to be affected by these vulnerabilities. Top of the section Close Section Details Cisco Unified Communications Manager (CUCM), formerly CallManager, is the call processing component of the Cisco IP Telephony solution that extends enterprise telephony features and functions to packet telephony network devices, such as IP phones, media processing devices, voice-over-IP (VoIP) gateways, and multimedia applications. SIP INVITE UDP Denial of Service: The CUCM Session Initiation Protocol (SIP) stack contains a DoS vulnerability. By flooding a CUCM system with normal SIP INVITE messages to UDP port 5060, it may be possible to trigger a resource exhaustion condition that will result in a kernel panic. This vulnerability is corrected in CUCM versions 5.1(2b), 5.1(3) and 6.0(1). This issue is documented in Cisco bug ID CSCsi75822. Centralized TFTP File Locator Service Overflow: The CUCM TFTP service contains a buffer overflow vulnerability in the processing of filenames that may allow a remote, unauthenticated user to cause a DoS condition or execute arbitrary code. The TFTP service serves files via two methods: traditional TFTP (UDP port 69), and a HTTP server that listens on TCP port 6970. The HTTP server component is known as the Centralized TFTP File Locator Service. The Centralized TFTP File Locator Service allows CUCM administrators to store device configuration and software files in a central location. The Centralized TFTP File Locator Service becomes active when the CUCM TFTP service is enabled and an alternate TFTP path is configured. Please consult the following documentation for more information on configuring the Centralized TFTP File Locator Service and alternate TFTP paths: http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_administration_ guide_chapter09186a008037e280.html#wp1044917 The overflow vulnerability only affects the Centralized TFTP File Locator Service component of the CUCM TFTP service. The Centralized TFTP File Locator Service is only used for communication between CUCM systems. The CUCM TFTP service is not enabled by default. This vulnerability is corrected in CUCM versions 5.1(2), 5.1(3) and 6.0(1). This issue is documented in Cisco bug ID CSCsh47712. Top of the section Close Section Vulnerability Scoring Details Cisco is providing 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. Cisco will provide a base and temporal score. Customers can then compute environmental scores to assist in determining the impact of the vulnerability in individual networks. CVSS is a standards based scoring method that conveys vulnerability severity and helps determine urgency and priority of response. 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. CSCsi75822 - CUCM SIP INVITE UDP Denial of Service ( registered customers only) Calculate the environmental score of CSCsi75822 CVSS Base Score - 7.8 Access Vector Access Complexity Authentication Confidentiality Impact Integrity Impact Availability Impact Network Low None None None Complete CVSS Temporal Score - 6.4 Exploitability Remediation Level Report Confidence Functional Official-Fix Confirmed CSCsh47712 - CUCM Centralized TFTP File Locator Service Overflow ( registered customers only) Calculate the environmental score of CSCsh47712 CVSS Base Score - 10 Access Vector Access Complexity Authentication Confidentiality Impact Integrity Impact Availability Impact Network Low None Complete Complete Complete CVSS Temporal Score - 8.3 Exploitability Remediation Level Report Confidence Functional Official-Fix Confirmed Top of the section Close Section Impact Successful exploitation of these vulnerabilities may result in a DoS condition. The TFTP service overflow vulnerability may also provide the ability to execute arbitrary code. Top of the section Close Section Software Versions and Fixes 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. Top of the section Close Section Workarounds There are no workarounds for these vulnerabilities. Filtering traffic to affected CUCM systems on screening devices can provide a mitigation technique for both vulnerabilities: Permit access to UDP port 5060 only from valid SIP devices to mitigate the SIP INVITE UDP DoS. Anti-spoofing measures should also be employed to prevent UDP spoofing. Permit access to TCP port 6970 only from CUCM systems to mitigate the Centralized TFTP File Locator Service overflow. There is currently no method to configure filtering directly on a CUCM system. Filters that deny SIP packets using UDP port 5060 and HTTP packets on TCP port 6970 should be deployed throughout the network as part of a transit access control list (tACL) policy for protection of traffic that enters the network at ingress access points. Filters for SIP packets using UDP port 5060 and HTTP packets on TCP port 6970 should be deployed in front of vulnerable network devices so that traffic is allowed from trusted clients only. Additional information about tACLs is available in Transit Access Control Lists: Filtering at Your Edge: http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_ paper09186a00801afc76.shtml Additional mitigations that can be deployed on Cisco devices within the network are available in the Cisco Applied Intelligence companion document for this advisory: http://www.cisco.com/warp/public/707/cisco-air-20071017-cucm.shtml Top of the section Close Section Obtaining Fixed Software Cisco will make free software available to address this vulnerability for affected customers. This advisory will be updated as fixed software becomes available. 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/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. Do not contact either "psirt@cisco.com" or "security-alert@cisco.com" for software upgrades. Fixed software for CUCM can be obtained here: http://www.cisco.com/pcgi-bin/tablebuild.pl/callmgr-51?psrtdcat20e2 ( registered customers only) The vulnerabilities contained in this advisory were first fixed in CUCM versions 5.1(2) and 5.1(2b) respectively. Customers who are not using the SIP protocol for voice communications can opt to upgrade to CUCM version 5.1(2) to obtain the fix for the TFTP vulnerability; however, Cisco recommends upgrading to the latest CUCM code to take advantage of fixed software. Customers using SIP are encouraged to upgrade to CUCM version 5.1(2b) or later. Top of the section Close Section 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. Top of the section Close Section 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 guidance and assistance with the appropriate course of action in regards to this advisory. The effectiveness of any workaround or fix 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 or fix is the most appropriate for use in the intended network before it is deployed. Top of the section Close Section 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. 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. Top of the section Close Section Exploitation and Public Announcements The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory. These vulnerabilities were discovered internally by Cisco. Top of the section Close Section Status of this Notice: FINAL 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. Top of the section Close Section Distribution This advisory is posted on Cisco's worldwide website at : http://www.cisco.com/warp/public/707/cisco-sa-20071017-cucm.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 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. Top of the section Close Section Revision History Revision 1.0 2007-Oct-17 Initial public release [***** End Cisco Security Advisory Document ID: 98833 *****] _______________________________________________________________________________ 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. 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