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Date : Fri, 23 May 2008 16:56:43 +0200
Type : VULN
Sujet : CERT-Renater : 2007/VULN176 (Cisco: Cisco Service Control Engine Denial of Service Vulnerabilities)
====================================================================                                    CERT-Renater

                         Note d'Information No. 2007/VULN176
_____________________________________________________________________

DATE                      : 23/05/2007

HARDWARE PLATFORM(S)      : SCE 1000 and 2000 series devices.

OPERATING SYSTEM(S)       : Cisco SCOS software.

======================================================================

Cisco Security Advisory: Cisco Service Control Engine Denial of Service
Vulnerabilities

Advisory ID: cisco-sa-20080521-sce

http://www.cisco.com/warp/public/707/cisco-sa-20080521-sce.shtml

Revision 1.0

For Public Release 2008 May 21 1600 UTC (GMT)

Summary
=======

Three Secure Shell (SSH) vulnerabilities exist in the Cisco Service
Control Engine (SCE) that may result in system instability or a reload
of the SCE. The first vulnerability may be triggered during SSH login
activity that is conducted within aggressive time frames. The second
vulnerability may be triggered with normal SSH login activity in
combination with other SCE management actions occurring simultaneously.
The third vulnerability may be triggered during SSH login and is
specific to the usage of unique invalid authentication credentials.

Cisco has made free upgrade software available to address these
vulnerabilities for affected customers. There are no workarounds for
these vulnerabilities.

Note: These vulnerabilities are independent of each other; a device may
be affected by one vulnerability and not by the others.

This advisory is posted at
http://www.cisco.com/warp/public/707/cisco-sa-20080521-sce.shtml.

Affected Products
=================

Vulnerable Products
+------------------

The SCE 1000 and 2000 series devices are affected by the following
vulnerabilities if the SSH server on the SCE is enabled:

   * System vulnerability to SSH login activity - affects SCE software
     versions prior to 3.1.6.
   * SSH login activity leads to illegal Input/Output operations -
     affects SCE software versions prior to 3.0.7 and 3.1.0.
   * SCE SSH authentication sequence anomaly - affects SCE software
     versions prior to 3.1.6.

Note: The SCE SSH server is disabled by default.

To determine whether you are running a vulnerable version of Cisco
Service Control Operating System (SCOS) software, issue the "Show
Version" command-line interface (CLI) command. The following example
shows a Cisco SCE that runs software release 3.1.6:

     SCE2000#>show version
     System version: Version 3.1.6 Build 157
     Build time: Mar 31 2008, 18:58:49 (Change-list 303626)
     Software version is: Version 3.1.6 Build 157


Products Confirmed Not Vulnerable
+--------------------------------

No other Cisco products are currently known to be affected by these
vulnerabilities.

Details
=======

Cisco SCE 1000 and 2000 series devices provide high-capacity advanced
application-level bandwidth optimization, stateful application
inspection, session-based classification and control of network
traffic. The SCE solution allows for the detection and control of
network applications including: web browsing, multimedia streaming, and
peer-to-peer (P2P).

This Security Advisory describes multiple distinct vulnerabilities.
These vulnerabilities are independent of each other.

   * System vulnerability to SSH login activity

A vulnerability impacting the SCE SSH server may be triggered during SSH
login activity, resulting in system instability or a reload of the SCE.
Specific SSH processes may encounter temporary resource unavailability
if called within aggressive intervals.

This vulnerability is documented in Cisco Bug ID CSCsi68582 and has been
assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2008-0534.

   * SSH login activity leads to illegal Input/Output operations

A second vulnerability exists in the SCE SSH server that may be
triggered with normal SSH traffic to the SCE management interface
occurring in conjunction with other management tasks. During this event,
an illegal IO operation may impact the SCE management agent, requiring a
reboot of the SCE to recover management access.

This vulnerability is documented in Cisco Bug ID CSCsh49563 and has been
assigned CVE ID CVE-2008-0536.

   * SCE SSH authentication sequence anomaly

A third vulnerability exists in the SCE SSH server that may also be
triggered during the SSH login process but unrelated to login attempt
frequency or other concurrent management tasks. This issue is triggered
by the usage of specific SSH credentials that attempt to change the
authentication method, resulting in an authentication sequence anomaly
impacting system stability.

This vulnerability is documented in Cisco Bug ID CSCsm14239 and has been
assigned CVE ID CVE-2008-0535.

Vulnerability Scoring Details
+----------------------------

Cisco has provided scores for the vulnerabilities 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
at

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.

* System vulnerability to SSH login activity (CSCsi68582)

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

* SSH login activity leads to illegal I/O operations (CSCsh49563)

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

* SCE SSH authentication sequence anomaly (CSCsm14239)

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 these vulnerabilities may result in the loss
of management access or, in some cases, cause vulnerable SCE devices to
reload.

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.

The following list contains the first fixed software release for each
vulnerability:

+---------------------------------------+
|                  | Affected |  First  |
|  Vulnerability   |  Major   |  Fixed  |
|                  | Release  | Release |
|------------------+----------+---------|
| System           | 1.x      | 3.1.6   |
|vulnerability to  |----------+---------|
| SSH login        | 2.x      | 3.1.6   |
|activity          |----------+---------|
|                  | 3.x      | 3.1.6   |
|------------------+----------+---------|
|                  | 1.x      | 3.0.7   |
|SSH login         |----------+---------|
| activity leads   | 2.x      | 3.0.7   |
|to illegal IO     |----------+---------|
| operations       | 3.x      | 3.0.7,  |
|                  |          | 3.1.0   |
|------------------+----------+---------|
|                  | 1.x      | 3.1.6   |
|SCE SSH           |----------+---------|
| authentication   | 2.x      | 3.1.6   |
|sequence anomaly  |----------+---------|
|                  | 3.x      | 3.1.6   |
+---------------------------------------+

SCOS software version 3.1.6 contains the fixes for all vulnerabilities
described in this document.

SCOS software is available for download from the following location on
cisco.com:

http://www.cisco.com/pcgi-bin/tablebuild.pl/scos?psrtdcat20e2

Workarounds
===========

There are no workarounds for these vulnerabilities.

Filtering SSH traffic with Access Control Lists (ACLs) to affected SCE
devices on the SCE management interface or on screening devices can
provide a mitigation technique for these vulnerabilities. Restricting
SCE SSH management interface access to only trusted devices through the
use of SCE ACLs or Transit ACLs is strongly recommended.

Additional information about SCE ACLs is available in the
"Configuring the Management Interface and Security" section of the
SCE Software Configuration Guide:

http://www.cisco.com/en/US/products/ps6134/products_configuration_guide_chapter09186a00808498b9.html#wp1060396

Additional information about tACLs is available in Transit Access
Control Lists: Filtering at Your Edge:

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_paper09186a00801afc76.shtml

Obtaining Fixed Software
========================

Cisco has released free software updates that address these
vulnerabilities. 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 vulnerabilities described in this advisory.

The SSH login activity vulnerability was discovered during the
resolution of customer support cases.

The illegal Input/Output operation and authentication sequence anomaly
were discovered by Cisco during internal testing.

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-20080521-sce.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-teams@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-21  | 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.

+--------------------------------------------------------------------
Copyright 2007-2008 Cisco Systems, Inc. All rights reserved.
+--------------------------------------------------------------------

Updated: May 21, 2008                             Document ID: 100706

+--------------------------------------------------------------------

======================================================================

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