__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Cisco Concentrator RADIUS PAP Authentication Vulnerability [Cisco Security Advisory - CSCdx82483] August 8, 2002 14:00 GMT Number M-106 ______________________________________________________________________________ PROBLEM: When a VPN 5000 series concentrator is configured to use a Remote Authentication Dial In User Service (RADIUS) server to authenticate client connections and the challenge type chosen is Password Authentication Protocol (PAP) or Challenge (a hybrid of PAP), the validation retry request sent to the RADIUS server when validation fails the first time does not have the user password field encrypted and so the password is sent as clear text. PLATFORM: All Cisco VPN 5000 series concentrator hardware running software release 6.0.21.0002 (and earlier) and 5.2.23.0003 (and earlier) DAMAGE: Since the password is sent in clear text it can easily be sniffed. SOLUTION: Apply workaround or upgrade software. ______________________________________________________________________________ VULNERABILITY The risk is HIGH. Sniffed passwords are frequently used to ASSESSMENT: easily gain access to systems. ______________________________________________________________________________ LINKS: CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/m-106l ORIGINAL BULLETIN: http://www.cisco.com/warp/public/707/vpn5k-radius-pap-vuln-pub.shtml ______________________________________________________________________________ [***** Start Cisco Security Advisory - CSCdx82483 *****] Cisco Security Advisory: Cisco VPN 5000 Series Concentrator RADIUS PAP Authentication Vulnerability Revision 1.0 For Public Release 2002 August 07 UTC 1500 -------------------------------------------------------------------------------- Please provide your feedback on this document. -------------------------------------------------------------------------------- Contents Summary Affected Products Details Impact Software Versions and Fixes Obtaining Fixed Software Workarounds Exploitation and Public Announcements Status of This Notice Distribution Revision History Cisco Security Procedures -------------------------------------------------------------------------------- Summary When a VPN 5000 series concentrator is configured to use a Remote Authentication Dial In User Service (RADIUS) server to authenticate client connections and the challenge type chosen is Password Authentication Protocol (PAP) or Challenge (a hybrid of PAP), the validation retry request sent to the RADIUS server when validation fails the first time does not have the user password field encrypted and so the password is sent as clear text. A VPN 5000 series concentrator configured to use Challenge-Handshake Authentication Protocol (CHAP) to authenticate is not affected by this vulnerability. This vulnerability is documented as Cisco bug ID CSCdx82483. There are workarounds available to mitigate the affects of this vulnerability. This advisory will be posted at http://www.cisco.com/warp/public/707/vpn5k-radius-pap- vuln-pub.shtml. Affected Products All Cisco VPN 5000 series concentrator hardware running software release 6.0.21.0002 (and earlier) and 5.2.23.0003 (and earlier) are affected by this vulnerability. This series includes models 5001, 5002, and 5008. The older IntraPort series concentrator hardware are also affected by this vulnerability. This series includes models IntraPort 2, IntraPort 2+, IntraPort Enterprise-2 and Enterprise-8, IntraPort Carrier-2, and Carrier-8. The VPN 3000 series concentrator hardware is not affected. No other Cisco product is currently known to be affected by this vulnerability. To determine your software revision, check the revision via the command line interface using the show version command. Details Cisco VPN 5000 series concentrator hardware running software release 6.0.21.0002 (and earlier) and 5.2.23.0003 (and earlier), accepting clients using PAP authentication, aggressive mode (AM), or hybrid IKE Extended Authentication (XAUTH) mode, and validating against a RADIUS server, are affected by this vulnerability. The VPN 5000 series concentrator supports three (3) RADIUS communication types. The [ RADIUS ] section keyword ChallengeType can be set to either CHAP, PAP, or Challenge. Challenge is a proprietary type of PAP used for Axent Defender authentication. In case PAP or Challenge is configured, the remote device sends an authentication request to the VPN 5000 series concentrator containing its name and password. The VPN 5000 series concentrator uses either its internal database or a RADIUS server to validate the request and returns an authentication success or failure packet. In the event that a RADIUS server is being used, the Access-Request is sent to the RADIUS server and the user password is encrypted as specified by the RFC. If the Access-Accept packet is not returned in a specific time, due to network or configuration problems, the concentrator sends out a retry packet but the user password is sent as clear text in this retry packet. This vulnerability is documented as Cisco bug ID CSCdx82483, which requires a CCO account to view and can be viewed after 2002 August 8 at 1500 UTC. Impact During the password validation against a RADIUS server the PAP authentication password, in retry packets, is sent in the clear instead of being encrypted. This allows the password to be sniffed off the network(s) connecting the VPN 5000 series concentrator and the RADIUS server. Software Versions and Fixes This vulnerability has been fixed in software release 6.0.21.0003 (and later) and 5.2.23.0004 (and later). The procedure to upgrade to the fixed software version is detailed at http://www.cisco.com/univercd/cc/td/doc/product/aggr/vpn5000/5000sw/conce60x/5000cfg/s winst.htm. Obtaining Fixed Software Cisco is offering free software upgrades to address this vulnerability for all affected customers. Customers may only install and expect support for the feature sets they have purchased. Customers with service contracts should contact their regular update channels to obtain the free software upgrade identified via this advisory. For most customers with service contracts, this means that upgrades should be obtained through the Software Center on Cisco's worldwide website at http://www.cisco.com/public/sw-center/. Customers whose Cisco products are provided or maintained through a 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 free software upgrade(s). Customers who purchased directly 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 obtain fixed software 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 advisory as evidence of your entitlement to a free upgrade. Please do not contact either "psirt@cisco.com" or "security-alert@cisco.com" for software upgrades. Workarounds One workaround is to only use CHAP for authentication by setting ChallengeType = CHAP in the [ RADIUS ] section. If you have to use PAP for authentication you can set the PrimRetries keyword to a value of 1 in the Radius section of the configuration. This would disable any retry attempts. Also, if a second (backup) RADIUS server is defined with SecAddress, it must be removed as the first attempt to a secondary RADIUS server will have the password in the clear. For a complete fix please 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 vulnerability described in this advisory. This vulnerability was reported to PSIRT by a customer. Status of This Notice: FINAL This is a final notice. 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/vpn5k-radius-pap-vuln-pub.shtml. In addition to worldwide website posting, a text version of this advisory is clear- signed with the Cisco PSIRT PGP key having the fingerprint FEB1 1B89 A64B 60BB 4770 D1CE 93D2 FF06 F236 759C and is posted to the following e-mail and Usenet news recipients: cust-security-announce@cisco.com bugtraq@securityfocus.com firewalls@lists.gnac.com first-teams@first.org (includes CERT/CC) cisco@spot.colorado.edu cisco-nsp@puck.nether.net comp.dcom.sys.cisco 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 Revision 1.0 2002-August-07 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/warp/public/707/sec_incident_response.shtml. This includes instructions for press inquiries regarding Cisco security notices. All Cisco Security Advisories are available at http://www.cisco.com/go/psirt. -------------------------------------------------------------------------------- This notice is Copyright 2002 by Cisco Systems, Inc. This notice may be redistributed freely after the release date given at the top of the text, provided that redistributed copies are complete and unmodified, and include all date and version information. -------------------------------------------------------------------------------- [***** End Cisco Security Advisory - CSCdx82483 *****] _______________________________________________________________________________ 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. 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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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