[NEWS] Content Switching Module DoS Vulnerabilities

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Content Switching Module DoS Vulnerabilities


The Cisco Content Switching Modules (CSM) and Cisco Content Switching
Module with SSL (CSM-S) contain two vulnerabilities that can lead to a
denial of service (DoS) condition. The first vulnerability exists when
processing TCP packets, and the second vulnerability affects devices with
service termination enabled.


Affected Products:
Vulnerable Products
These vulnerabilities were identified in CSM software version 4.2 and
CSM-S software version 2.1. The following table helps illustrate the
vulnerable software versions for these products:

Vulnerability - CSM - CSM-S
* TCP packet Processing DOS - 4.2 Prior to 4.2.3a - 2.1 Prior to 2.1.2a
* Service Termination - 4.2 Prior to 4.2.7 - 2.1 Prior to 2.1.6

To determine the software running on a Content Switching Module, log in to
the Catalyst switch and issue the show version command.

The following example shows a CSM running software version 4.2(2) in a
Supervisor running CatOS. Supervisors running CatOS or IOS will have
similar output. The version of the CSM is shown on the module labeled
WS-X6066-SLB-APC as illustrated in the following output.

Console>show version
WS-C6506 Software, Version NmpSW: 7.6(9)
Copyright (c) 1995-2004 by Cisco Systems
NMP S/W compiled on Aug 27 2004, 20:05:14

System Bootstrap Version: 7.1(1)
System Boot Image File is 'disk0:cat6000-sup2k8.7-6-9.bin'
System Configuration register is 0x2102

Hardware Version: 3.0 Model: WS-C6506 Serial #: TBA05360375

PS1 Module: WS-CAC-1300W Serial #: ACP05061071
PS2 Module: WS-CAC-1300W Serial #: ACP05060407

Mod Port Model Serial # Versions
--- ---- ------------------- -----------
1 2 WS-X6K-SUP2-2GE SAD055104YY Hw : 3.2
Fw : 7.1(1)
Fw1: 6.1(3)
Sw : 7.6(9)
Sw1: 7.6(9)
WS-F6K-PFC2 SAD055104H5 Hw : 3.0
Sw :
WS-X6K-SUP2-2GE SAD055104YY Hw : 3.2
Sw :
2 48 WS-X6248-RJ-45 SAD0501084U Hw : 1.4
Fw : 5.4(2)
Sw : 7.6(9)

5 4 WS-X6066-SLB-APC SAD105003DW Hw : 1.9
Fw :
Sw : 4.2(2)

Module Total Used Free Total Used Free Total Used
------ ------- ------- ------- ------- ------- ------- ----- -----
1 262144K 70354K 191790K 32768K 23251K 9517K 512K 253K

Uptime is 43 days, 22 hours, 7 minutes

The following configuration segment shows a vserver with service
terminations enabled:

vserver WWW:2
virtual x.x.x.x tcp www service termination

Products Confirmed Not Vulnerable
Only Catalyst CSM modules running indicated 4.2 versions are affected by
these vulnerabilities. CSM software versions 4.1, 3.2 and 3.1 are not
affected by these vulnerabilities.

Catalyst CSM-S modules running indicated 2.1 versions are the only
vulnerable versions of software for that product.

No other Cisco products are currently known to be affected by this
vulnerability. The Cisco Secure Content Accelerator is not affected by
this vulnerability.

The Catalyst CSM is an integrated Server Load Balancing line card for the
Catalyst 6500 and 7600 Series designed to enhance the response time for
client traffic to end points including servers, caches, firewalls, Secure
Sockets Layer (SSL) devices, and VPN termination devices.

The Catalyst 6500 CSM-S combines high-performance server load balancing
(SLB) with Secure Socket Layer (SSL) offload. The CSM-S is similar to the
CSM; however, it can also terminate and initiate SSL-encrypted traffic,
which allows the CSM-S to perform intelligent load balancing while
ensuring secure end-to-end encryption.

When a module running affected code receives specific TCP packets out of
order, a DoS condition may be triggered resulting in the CPU reaching 100%
utilization or a reload with a FPGA4 exception with icp.fatPath length

This vulnerability is documented in Cisco bug ID
<http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCsd27478> CSCsd27478 ( registered customers only) .

When service termination is enabled on a module running affected software
and the module is under high network utilization, a DoS condition may be
triggered, resulting in a reload with a FPGA4 exception 1 IDLE error.

This vulnerability is documented in Cisco bug ID
<http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCsh57876> CSCsh57876 ( registered customers only) .

In normal operations, the MSFC CLI handles the management of the CSM and
CSM-S; however, in order to upgrade the software, a user must first log
into the switch and session to the module.

For more information on how to upgrade your CSM, visit the
<http://www.cisco.com/en/US/products/hw/modules/ps2706/products_tech_note09186a0080094526.shtml> http://www.cisco.com/en/US/products/hw/modules/ps2706/products_tech_note09186a0080094526.shtml page on Cisco.com.

Information on how to upgrade the CSM-S can be found at:
<http://www.cisco.com/en/US/docs/interfaces_modules/services_modules/csms/2.1.1/configuration/guide/getstart.html#wp1041858> http://www.cisco.com/en/US/docs/interfaces_modules/services_modules/csms/2.1.1/configuration/guide/getstart.html#wp1041858.

Successful exploitation of these vulnerabilities against a system running
a vulnerable version of CSM or CSM-S software may cause the system to
become unresponsive or reload. Repeated attacks may result in a prolonged
DoS condition.

Software Versions and Fixes
When considering software upgrades, also consult
<http://www.cisco.com/go/psirt> http://www.cisco.com/go/psirt and any
subsequent advisories to determine exposure and a complete upgrade

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

For more information on the terms "Rebuild" and "Maintenance," consult the
following URL:
<http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_white_paper09186a008018305e.shtml> http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_white_paper09186a008018305e.shtml.

Registered customers can obtained fixed software for the CSM from:
http://www.cisco.com/pcgi-bin/tablebuild.pl/cat6000-csm?psrtdcat20e2 (
registered customers only)

Registered customers can obtained fixed software for the CSM-S from:
http://www.cisco.com/pcgi-bin/tablebuild.pl/cat6000-csms?psrtdcat20e2 (
registered customers only)

There are no workarounds for these vulnerabilities. Removing service
termination will mitigate Cisco bug ID CSCsh57876; however, disabling this
feature disables services that may be critical to the operation of the

Additional mitigations that can be deployed on Cisco devices within the
network are available in the Cisco Applied Intelligence companion document
for this advisory:



The information has been provided by <mailto:psirt@xxxxxxxxx> Cisco
Systems Product Security Incident Response Team.
The original article can be found at:


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