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AUSCERT External Security Bulletin Redistribution
ESB-2008.0504 -- [Cisco]
Cisco Content Switching Module Memory Leak Vulnerability
15 May 2008
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Content Switching Module
Publisher: Cisco Systems
Operating System: Cisco
Impact: Denial of Service
Access: Remote/Unauthenticated
CVE Names: CVE-2008-1749
Original Bulletin:
http://www.cisco.com/warp/public/707/cisco-sa-20080514-csm.shtml
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Cisco Security Advisory: Cisco Content Switching Module Memory Leak
Vulnerability
Advisory ID: cisco-sa-20080514-csm
http://www.cisco.com/warp/public/707/cisco-sa-20080514-csm.shtml
Revision 1.0
For Public Release 2008 May 14 1600 UTC (GMT)
Summary
=======
The Cisco Content Switching Module (CSM) and Cisco Content Switching
Module with SSL (CSM-S) contain a memory leak vulnerability that can
result in a denial of service condition. The vulnerability exists when
the CSM or CSM-S is configured for layer 7 load balancing. An attacker
can trigger this vulnerability when the CSM or CSM-S processes TCP
segments with a specific combination of TCP flags while servers behind
the CSM/CSM-S are overloaded and/or fail to accept a TCP connection.
Cisco has released free software updates that address this
vulnerability.
This advisory is posted at
http://www.cisco.com/warp/public/707/cisco-sa-20080514-csm.shtml.
Affected Products
=================
Vulnerable Products
+------------------
The Cisco CSM and Cisco CSM-S are affected by the vulnerability
described in this document if they are running an affected software
version and are configured for layer 7 load balancing.
The following versions of the Cisco CSM software are affected by this
vulnerability: 4.2(3), 4.2(3a), 4.2(4), 4.2(5), 4.2(6), 4.2(7), and
4.2(8).
The following versions of the Cisco CSM-S software are also affected by
this vulnerability: 2.1(2), 2.1(3), 2.1(4), 2.1(5), 2.1(6), and 2.1(7).
To determine the software version in use by the CSM or CSM-S, log into
the supervisor of the chassis that hosts the CSM or CSM-S modules and
issue the command "show module version" (Cisco IOS) or "show version"
(Cisco CatOS). CSM modules will display as model "WS-X6066-SLB-APC",
CSM-S modules will display as model "WS-X6066-SLB-S-K9", and the
software version will be indicated next to the "Sw:" label.
Note that the output from "show module version" (for Cisco IOS) is
slightly different from the output from "show version" (for Cisco
CatOS). However, in both cases the model names will read as previously
described, and the software version will be easily identified by looking
for the "Sw:" label.
The following example shows a CSM in slot number 4 running software
version 4.2(3):
switch>show module version
Mod Port Model Serial # Versions
+--- ---- ------------------ ----------- -------------------------------------
1 3 WS-SVC-AGM-1-K9 SAD092601W5 Hw : 1.0
Fw : 7.2(1)
Sw : 5.0(3)
2 6 WS-SVC-FWM-1 SAD093200X8 Hw : 3.0
Fw : 7.2(1)
Sw : 3.2(3)1
3 8 WS-SVC-IDSM-2 SAD0932089Z Hw : 5.0
Fw : 7.2(1)
Sw : 5.1(6)E1
4 4 WS-X6066-SLB-APC SAD093004BD Hw : 1.7
Fw :
Sw : 4.2(3)
5 2 WS-SUP720-3B SAL0934888E Hw : 4.4
Fw : 8.1(3)
Sw : 12.2(18)SXF11
Sw1: 8.6(0.306)R3V15
WS-SUP720 SAL09348488 Hw : 2.3
Fw : 12.2(17r)S2
Sw : 12.2(18)SXF11
WS-F6K-PFC3B SAL0934882R Hw : 2.1
A Cisco CSM or CSM-S is configured for layer 7 load balancing if one or
more layer 7 Server Load Balancing (SLB) policies are referenced in the
configuration of a virtual server. There are six possible types of SLB
policies: "client-group", "cookie-map", "header-map", "reverse-sticky",
"sticky-group", and "url-map". Of these, the "client-group" policy
type is always a layer 4 policy. The remaining policy types are
layer 7 policies and, if used, would render a device affected by the
vulnerability described in this document. The following example shows a
CSM module that is configured for layer 7 load balancing. Note the SLB
policy "TEST-SPORTS-50", which uses "url-map" and "header-map" layer 7
policies, and that is applied to the virtual server named "WEB":
module ContentSwitchingModule 5
[...]
!
policy TEST-SPORTS-50
url-map SPORTS
header-map TEST
client-group 50
serverfarm WEBFARM2
!
vserver WEB
virtual 10.20.221.100 tcp www
serverfarm WEBFARM
persistent rebalance
slb-policy TEST-SPORTS-50
inservice
Products Confirmed Not Vulnerable
+--------------------------------
Only Cisco CSM modules running indicated 4.2 versions are affected by
this vulnerability. CSM software versions 4.1, 3.2 and 3.1 are not
affected by this vulnerability.
Cisco CSM-S modules running indicated 2.1 versions are the only
vulnerable versions of software for that product.
Cisco CSM and CSM-S modules that are not configured for layer 7 load
balancing are not affected by this vulnerability.
The Cisco IOS SLB feature is not affected by this vulnerability.
No other Cisco products are currently known to be affected by this
vulnerability. The Cisco Secure Content Accelerator is not affected by
this vulnerability.
Details
=======
The Cisco CSM is an integrated SLB line card for the Catalyst 6500 and
7600 Series that is 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 Cisco CSM-S combines high-performance SLB with SSL offload. The
CSM-S is similar to the CSM; however, unlike the CSM, the CSM-S can
terminate and initiate SSL-encrypted traffic. This ability allows the
CSM-S to perform intelligent load balancing while ensuring secure
end-to-end encryption.
A memory leak vulnerability exists in some versions of the software
for the Cisco CSM and Cisco CSM-S when the CSM or CSM-S is configured
for layer 7 load balancing (see the "Vulnerable Products" section for
configuration details). The memory leak is triggered when the CSM or
CSM-S processes TCP segments with a specific combination of TCP flags
and fails to make a load balancing decision because servers behind the
CSM/CSM-S are overloaded and/or fail to accept a TCP connection.
The memory leak can be detected by issuing the command "show module
ContentSwitchingModule <slot #> tech-support all | include Outstanding"
on the supervisor and checking the command output for a high number of
outstanding buffers as seen in the following example:
switch#show module ContentSwitchingModule 10 tech-support all | include Outstanding
Outstanding slowpath(low pri) buffers 0 0
Outstanding slowpath(high pri) buffers 0 0
Outstanding blocks 0 0
Outstanding small buffers 0 0
Outstanding medium buffers 823 0
Outstanding large buffers 0 0
Outstanding sessions 0 0
Outstanding Closes 0 0
Close Relinquish Outstanding 0
Because small, medium, and large buffers can be affected by the memory
leak, administrators are advised to check the number of these buffers in
the output from the preceding command to accurately detect a memory leak
condition.
This vulnerability is documented in Cisco Bug ID CSCsl40722 and has been
assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2008-1749.
Vulnerability Scoring Details
+----------------------------
Cisco has provided scores for the vulnerability in this advisory based
on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in
this Security Advisory is done in accordance with CVSS version 2.0.
CVSS is a standards-based scoring method that conveys vulnerability
severity and helps determine urgency and priority of response.
Cisco has provided a base and temporal score. Customers can then
compute environmental scores to assist in determining the impact of the
vulnerability in individual networks.
Cisco has provided an FAQ to answer additional questions regarding VSS
Cat
http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html.
Cisco has also provided a CVSS calculator to help compute the
environmental impact for individual networks at
http://intellishield.cisco.com/security/alertmanager/cvss.
* CSM: Potential buffer loss with irregular client streams (CSCsl40722)
CVSS Base Score - 7.8
Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - None
Integrity Impact - None
Availability Impact - Complete
CVSS Temporal Score - 6.4
Exploitability - Functional
Remediation Level - Official-Fix
Report Confidence - Confirmed
Impact
======
Successful exploitation of this vulnerability against a system running
a vulnerable version of the Cisco CSM or the Cisco CSM-S software may
cause the CSM or CSM-S to stop passing traffic. Repeated attacks may
result in a prolonged DoS condition, which could affect the services
that are offered by the end point devices behind the CSM or CSM-S.
Note that the supervisor or any other non-CSM or non-CSM-S service
module in the same chassis of the Catalyst 6500 switch or 7600 Series
router that hosts the CSM or CSM-S will not be affected by this
vulnerability.
Software Versions and Fixes
===========================
When considering software upgrades, also consult
http://www.cisco.com/go/psirt and any subsequent advisories to determine
exposure and a complete upgrade solution.
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 assistance.
This vulnerability is fixed in version 4.2.9 of the Cisco CSM software,
and in version 2.1.8 of the Cisco CSM-S software.
CSM software can be downloaded from
http://www.cisco.com/pcgi-bin/tablebuild.pl/cat6000-csm?psrtdcat20e2.
Information on how to upgrade the CSM software is available at
http://www.cisco.com/en/US/products/hw/modules/ps2706/products_tech_note09186a0080094526.shtml.
CSM-S software can be downloaded from
http://www.cisco.com/pcgi-bin/tablebuild.pl/cat6000-csms?psrtdcat20e2.
Information on how to upgrade the CSM-S software is available at
http://www.cisco.com/en/US/docs/interfaces_modules/services_modules/csms/2.1.1/configuration/guide/getstart.html#wp1041858.
Workarounds
===========
There are no workarounds for this vulnerability. When the Cisco CSM or
Cisco CSM-S has run out of memory it will simply stop passing traffic
and it will have to be reloaded. The CSM and CSM-S can be reloaded via
the command "hw-module module <CSM or CSM-S slot number> reset" (Cisco
IOS) or via the command "reset <CSM or CSM-S slot number>" (Cisco CatOS)
from the privileged EXEC prompt of the supervisor. There is no need to
reload the supervisor.
Obtaining Fixed Software
========================
Cisco has released free software updates that address this
vulnerability. Prior to deploying software, customers should consult
their maintenance provider or check the software for feature set
compatibility and known issues specific to their environment.
Customers may only install and expect support for the feature sets
they have purchased. By installing, downloading, accessing or
otherwise using such software upgrades, customers agree to be bound
by the terms of Cisco's software license terms found at
http://www.cisco.com/en/US/products/prod_warranties_item09186a008088e31f.html,
or as otherwise set forth at Cisco.com Downloads at
http://www.cisco.com/public/sw-center/sw-usingswc.shtml.
Do not contact psirt@cisco.com or security-alert@cisco.com for software
upgrades.
Customers with Service Contracts
+-------------------------------
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
website at http://www.cisco.com.
Customers using Third Party Support Organizations
+------------------------------------------------
Customers whose Cisco products are provided or maintained through prior
or existing agreements with third-party support organizations, such
as Cisco Partners, authorized resellers, or service providers should
contact that support organization for guidance and assistance with the
appropriate course of action in regards to this advisory.
The effectiveness of any workaround or fix is dependent on specific
customer situations, such as product mix, network topology, traffic
behavior, and organizational mission. Due to the variety of affected
products and releases, customers should consult with their service
provider or support organization to ensure any applied workaround or fix
is the most appropriate for use in the intended network before it is
deployed.
Customers without Service Contracts
+----------------------------------
Customers who purchase direct from Cisco but do not hold a Cisco service
contract, and customers who purchase through third-party vendors but are
unsuccessful in obtaining fixed software through their point of sale
should acquire 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
Customers should have their product serial number available and be
prepared to give the URL of this notice as evidence of entitlement to a
free upgrade. Free upgrades for non-contract customers must be requested
through the TAC.
Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml
for additional TAC contact information, including localized telephone
numbers, and instructions and e-mail addresses for use in various
languages.
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 discovered during the investigation of customer
support cases.
Status of this Notice: FINAL
============================
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY
ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE
INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS
AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS
DOCUMENT AT ANY TIME.
A stand-alone copy or Paraphrase of the text of this document 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 is posted on Cisco's worldwide website at:
http://www.cisco.com/warp/public/707/cisco-sa-20080514-csm.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
* first-bulletins@first.org
* bugtraq@securityfocus.com
* vulnwatch@vulnwatch.org
* cisco@spot.colorado.edu
* cisco-nsp@puck.nether.net
* full-disclosure@lists.grok.org.uk
* comp.dcom.sys.cisco@newsgate.cisco.com
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 | 2008-May-14 | 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/en/US/products/products_security_vulnerability_policy.html.
This includes instructions for press inquiries regarding Cisco security
notices. All Cisco security advisories are available at
http://www.cisco.com/go/psirt.
+--------------------------------------------------------------------
All contents are Copyright (C) 2007-2008 Cisco Systems, Inc. All
rights reserved.
+--------------------------------------------------------------------
Updated: May 14, 2008 Document ID: 105450
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