__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Center ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Cisco VPN3000 Concentrator TELNET Vulnerability April 6, 2001 19:00 GMT Number L-068 ______________________________________________________________________________ PROBLEM: The SSL and telnet connections are not handled properly for failed logon attempts. PLATFORM: Cisco VPN 3000 series concentrators running software releases up to but not including version 3.0.00 are affected by this vulnerability. This series includes models 3005, 3015, 3030, 3060, and 3080. DAMAGE: A flood of data sent to either the SSL or telnet port can cause Cisco VPN 3000 series concentrators to reboot. The concentrator will reboot each time the port is flooded with data. This results in a denial of service (DoS) condition. SOLUTION: To determine if a Cisco VPN 3000 series concentrator is running affected software, check version via the web interface or the console login. If the system requires patching, follow Cisco instructions for obtaining the patch. ______________________________________________________________________________ VULNERABILITY The risk is LOW. There have been no reports of this DoS in the ASSESSMENT: wild. ______________________________________________________________________________ [****** Begin Cisco Bulletin ******] Cisco Security Advisory: VPN3000 Concentrator TELNET Vulnerability ========================================================================== Revision 1.0 For Public Release 2001 March 28 08:00 (UTC -0800) ------------------------------------------------------------------------ Summary ======= Sending a flood of data to the SSL or regular telnet port can cause the Cisco VPN 3000 series concentrators to reboot. After rebooting, the equipment would function normally until the flood of data is sent again. To remove the vulnerability, Cisco is offering free software upgrades to revision 3.0.00 for all affected platforms. The defect is described in DDTS record CSCds90807. This notice will be posted at http://www.cisco.com/warp/public/707/vpn3k-telnet-vuln-pub.shtml Affected Products ================= Cisco VPN 3000 series concentrators running software releases up to but not including version 3.0.00 are affected by this vulnerability. This series includes models 3005, 3015, 3030, 3060, and 3080. Any model running version 3.0.00 or later is unaffected. This vulnerability does not affect the VPN 5000 series concentrators. No other Cisco product is affected by this vulnerability. To determine if a Cisco VPN 3000 series concentrator is running affected software, check version via the web interface or the console login. Details ======= The vulnerability occurs because the SSL or regular telnet session does not disconnect after repeated failed attempts and the system keeps trying to interpret the data coming in on the SSL or regular telnet port. Therefore, data coming in at an uncontrolled rate can flood the telnet queues causing a shortage of memory on the system resulting in a reboot. This has been fixed by ensuring that a SSL or regular telnet session is terminated after three repeated failed attempts. The vulnerability is documented as DDTS CSCds90807 Impact ====== Sending a flood of data to the SSL or regular telnet port can cause the VPN 3000 series concentrators to reboot. While reloading, the device cannot handle any traffic. Repeatedly causing the affected device to reload will result in a denial of service, thus affecting the availability of the device. SSL and regular telnet service on the external interface is disabled by default. Software Versions and Fixes =========================== The vulnerability has been fixed in revision 3.0.00 code. The fix will be carried forward into all future releases. Obtaining Fixed Software ======================== Cisco is offering free software upgrades to eliminate this vulnerability for all affected customers. Customers with contracts should obtain upgraded software through their regular update channels. For most customers, this means that upgrades should be obtained via Cisco's Software Center at http://www.cisco.com/. Customers without contracts or warranty should get their upgrades by contacting the Cisco Technical Assistance Center (TAC) as shown below: * (800) 553-2447 (toll-free in 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 instructions and e-mail addresses for use in various languages. 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. Please do not contact either "psirt@cisco.com" or "security-alert@cisco.com" for software upgrades; faster results will be obtained by contacting the TAC directly. Workarounds =========== The vulnerability can be avoided by disabling all Telnet access to the equipment until you upgrade. There are two ways to disallow telnet on any given interface - you can use a filter whose rules don't allow telnet, or by creating a rule that specifically denies telnet access and applying that to your existing filter(s). Further details can be found at the this URL http://www/univercd/cc/td/doc/product/vpn/vpn3000/vpn3kco/vcoug/usrguide/polmgt. htm After disabling SSL and regular telnet the equipment can be managed via the console port or via browser access. Exploitation and Public Announcements ===================================== The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerabilities described in this advisory. This was reported to Cisco by a customer who discovered this vulnerability as a side effect of using a SSL telnet tool. Status of This Notice: FINAL ============================ This is a final field notice. Although Cisco cannot guarantee the accuracy of all statements in this notice, all of the facts have been checked to the best of our ability. Cisco does not anticipate issuing updated versions of this notice unless there is some material change in the facts. Should there be a significant change in the facts, Cisco may update this notice. Distribution ============ This notice will be posted on Cisco's Worldwide Web site at http://www.cisco.com/warp/public/707/vpn3k-telnet-vuln-pub.shtml. In addition to Worldwide Web posting, a text version of this notice will be clear-signed with the Cisco PSIRT PGP key and will be 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 (including CERT/CC) * cisco@spot.colorado.edu * cisco-nsp@puck.nether.net * comp.dcom.sys.cisco * Various internal Cisco mailing lists Future updates of this notice, if any, will be placed on Cisco's Worldwide Web server, but may or may not be actively announced on mailing lists or newsgroups. Users concerned about this problem are encouraged to check the URL given above for any updates. Revision History Revision 2001-03-28Initial Public Release 1.0 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 Web site at http://www.cisco.com/warp/public/707/sec_incident_response.shtml. This includes instructions for press inquiries regarding Cisco security notices. ------------------------------------------------------------------------ This notice is Copyright 2001 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. ------------------------------------------------------------------------ All contents are Copyright © 1992--2001 Cisco Systems Inc. All rights reserved. Important Notices and Privacy Statement. [****** End Cisco Bulletin *****] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Cisco Systems, Inc. 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. 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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. LAST 10 CIAC BULLETINS ISSUED (Previous bulletins available from CIAC) L-057: Kerberos /tmp Root Vulnerability L-058: HPUX Sec. 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