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Cisco Security Advisory: Cisco IOS Software Layer 2 Tunneling
Protocol (L2TP) Denial of Service Vulnerability
Advisory ID: cisco-sa-20080924-l2tp
http://www.cisco.com/warp/public/707/cisco-sa-20080924-l2tp.shtml
Revision 1.0
For Public Release 2008 September 24 1600 UTC (GMT)
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Summary
======
A vulnerability exists in the Cisco IOS software implementation of
Layer 2 Tunneling Protocol (L2TP), which affects limited Cisco IOS
software releases.
Several features enable the L2TP mgmt daemon process within Cisco IOS
software, including but not limited to Layer 2 virtual private
networks (L2VPN), Layer 2 Tunnel Protocol Version 3 (L2TPv3), Stack
Group Bidding Protocol (SGBP) and Cisco Virtual Private Dial-Up
Networks (VPDN). Once this process is enabled the device is
vulnerable.
This vulnerability will result in a reload of the device when
processing a specially crafted L2TP packet.
Cisco has released free software updates that address this
vulnerability.
Workarounds that mitigate this vulnerability are available.
This advisory is posted at
http://www.cisco.com/warp/public/707/cisco-sa-20080924-l2tp.shtml
Note: The September 24, 2008 IOS Advisory bundled publication
includes twelve Security Advisories. Eleven of the advisories address
vulnerabilities in Cisco's IOS software, and one advisory addresses
vulnerabilities in Cisco Unified Communications Manager. Each
Advisory lists the releases that correct the vulnerability described
in the Advisory. Please reference the following software table to
find a release that fixes all published IOS software Advisories as of
September 24th, 2008:
http://www.cisco.com/warp/public/707/cisco-sa-20080924-bundle.shtml
Individual publication links are listed below:
* http://www.cisco.com/warp/public/707/cisco-sa-20080924-iosips.shtml
* http://www.cisco.com/warp/public/707/cisco-sa-20080924-ssl.shtml
* http://www.cisco.com/warp/public/707/cisco-sa-20080924-sip.shtml
* http://www.cisco.com/warp/public/707/cisco-sa-20080924-cucm.shtml
* http://www.cisco.com/warp/public/707/cisco-sa-20080924-vpn.shtml
* http://www.cisco.com/warp/public/707/cisco-sa-20080924-mfi.shtml
* http://www.cisco.com/warp/public/707/cisco-sa-20080924-ipc.shtml
* http://www.cisco.com/warp/public/707/cisco-sa-20080924-ubr.shtml
* http://www.cisco.com/warp/public/707/cisco-sa-20080924-multicast.shtml
* http://www.cisco.com/warp/public/707/cisco-sa-20080924-sccp.shtml
* http://www.cisco.com/warp/public/707/cisco-sa-20080924-iosfw.shtml
Affected Products
================
All devices running affected versions of 12.2 or 12.4 Cisco IOS
system software and that have a vulnerable configuration are affected
by this vulnerability.
Vulnerable Products
+------------------
To determine if a device is vulnerable, first confirm that the device
is running an affected version of 12.2 or 12.4 Cisco IOS system
software. Then check for the process L2TP mgmt daemon running on the
device.
To determine the software version running on a Cisco product, log in
to the device and issue the show version command to display the
system banner. Cisco IOS software will identify itself as
"Internetwork Operating System Software" or simply "IOS." On the next
line of output, the image name will be displayed between parentheses,
followed by "Version" and the IOS release name. Other Cisco devices
will not have the show version command or will give different output.
The following example identifies a Cisco product that is running
Cisco IOS Software Release 12.4(11)T2:
Router#show version
Cisco IOS Software, 7200 Software (C7200-ADVSECURITYK9-M), Version 12.4(11)T2, RELEASE SOFTWARE (fc4)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Tue 01-May-07 04:19 by prod_rel_team