From psirt@cisco.com Wed Dec 6 16:34:26 2000 From: Cisco Systems Product Security Incident Response Team To: BUGTRAQ@SECURITYFOCUS.COM Date: Wed, 6 Dec 2000 08:30:00 -0700 Subject: [BUGTRAQ] Cisco Security Advisory: Cisco Catalyst Memory Leak Vulnerability -----BEGIN PGP SIGNED MESSAGE----- Cisco Catalyst Memory Leak Vulnerability Revision 1.0 For Release 2000 December 6 08:00 AM US/Pacific (UTC+0700) _________________________________________________________________ Summary A series of failed telnet authentication attempts to the switch can cause the Catalyst Switch to fail to pass traffic or accept management connections until the system is rebooted or a power cycle is performed. All types of telnet authentication are affected, including Kerberized telnet, and AAA authentication. This vulnerability has been assigned Cisco bug ID CSCds66191. The complete advisory can be viewed at http://www.cisco.com/warp/public/707/catalyst-memleak-pub.shtml. Affected Products Catalyst 4000 and 5000 images running version 4.5(2) up to 5.5(4) and 5.5(4a). Catalyst 6000 images running version 5.3(1)CSX, up to and including 5.5(4), 5.5(4a). No other releases of Cisco Catalyst software are affected by this vulnerability. No other Cisco products are affected by this vulnerability. Details The telnet process fails to release resources upon a failed authentication, or a successful login of extremely short duration such as a telnet from within an automated script. This memory leak eventually results in the failure of the switch to perform any other processes, such as forwarding traffic or management; a power cycle or reboot is required for recovery. The command "show process memory" will indicate increased "Holding" memory after failed telnet authentication attempts. This value will not decrease over time except when a reboot, reload, or power cycle occurs. This bug may be triggered over a period of time in the course of normal operation by legitimate users that occasionally fail authentication. lt-6509-e> (enable) sh proc mem Memory Used: 3974544 Free: 15265168 Total: 19239712 PID TTY Allocated Freed Holding Process - ---------- ---------- ---------- ---------- ---------- --------------- 1 -2 1707632 3488 1704144 Kernel and Idle 24 -2 16 0 16 telnetd Impact This vulnerability enables a Denial of Service attack on the Catalyst switch. Software Versions and Fixes Cisco has made the following fixed software available to customers: Catalyst Release 4.5(10) for Catalyst 4000 and 5000. Catalyst Release 5.5(4b) for Catalyst 4000, 5000 and 6000. The fix will be carried forward into all future releases. Getting Fixed Software Cisco is offering free software upgrades to remedy 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 through the Software Center on Cisco's Worldwide Web site at http://www.cisco.com. Customers without contracts 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 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. Workarounds There is no configuration workaround to eliminate the problem. However, if you are unable to upgrade to an unaffected version, you may use other devices to strictly control or prohibit telnet access to the switch, permitting only connections from your local network. Access control lists on the switch can limit the remote exploitation of the vulnerability. To limit access to known hosts use the following commands: set ip permit enable telnet set ip permit [mask] Remote management of the switch can also be disabled. The above workarounds are provided as an option; however, the recommendation is to upgrade to fixed code as soon as possible. Exploitation and Public Announcements Cisco Systems knows of no public discussion nor active exploits involving this vulnerability, which was reported by a customer who noted the memory leak. 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/catalyst-memleak-pub.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 * bugtraq@securityfocus.com * first-teams@first.org (includes CERT/CC) * cisco@spot.colorado.edu * 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 1.006-DEC-2000 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 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 2000 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, including all date and version information. _________________________________________________________________ -----BEGIN PGP SIGNATURE----- Version: PGP 6.0.2 iQEVAwUBOi5pUmiN3BRdFxkbAQE7jwf6A21IUrXrGI1ZueXwaBymh2xVDfnKee4R KFybnDfNYTEAs5L5pE62x5QnL7xEQ+W5arZzmTKpxD9e+No7RUaSTVvUUJc5LIWn zMCGfUdiwVKKtMSWqJR7GApmlnhY0f5sw8e/pMZKmcN1f5ZArNEZjoTca9nr4l67 XEvC3A2iUS+olT33YSsAogqt7gPVY6WNRKKvkw0xuxzXm6LKnlVCPGqMYP6fcMrr 7Dpb8mwl/abJT5tAZ/bbuKj+EKfzsw6E7mSIKfCf6n3Q0+rzlMhn3sWd/IvrXJII Diw2o0HSvRkfMfIoVjchCYSU5Ph5BLF5bP9RpA6DwKTD3nRZEj3Cmw== =Hs5N -----END PGP SIGNATURE-----