[c-nsp] Cisco Security Advisory: Crafted Timed Attack Evades Cisco Security Agent Protections

Thu Nov 11 11:50:04 EST 2004

Cisco Security Agent (CSA) provides threat protection for server and
desktop computing systems, also known as endpoints.  It identifies and
prevents malicious behavior, thereby eliminating known and unknown
security risks.

A vulnerability exists in which a properly timed buffer overflow attack
may evade the protections offered by CSA.  The system under attack must
contain an unpatched underlying vulnerability in system software that
CSA is configured to protect.  Another prerequisite for the attack is
that a user must be interactively logged in during the attack.

This advisory is posted at 
http://www.cisco.com/warp/public/707/cisco-sa-20041111-csa.shtml

Cisco is making patches available for CSA versions 4.0 free of charge, to
correct the problem.

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

The following products are affected:

  * Cisco Security Agent versions up to and excluding 4.0.3 build 728
  * Cisco Security Agent 3.x versions
  * Okena Stormwatch 3.x versions

Determining the Version of the CSA client
- -----------------------------------------

To determine which version of CSA is running on client machines simply
right click on the CSA icon in the task bar. On the pop-up menu,
selecting "About ..." will display the version number of the agent.

Determining the Version on the CSA Management Console
- -----------------------------------------------------

To determine which version of CSA you are running log on to the Management
console for Cisco Security Agent on your CiscoWorks server:

http://ciscoworks-hostname:1741/

Select the Security Agents tab under

  * VPN/Security Management Solution
      + Management Center
          o Security Agents

This will launch the Management Center for Cisco Security Agents.  Within
the browser window, locate the tab in the center marked "Help" and click
on the sub-item labeled "About". The version of the Cisco Security Agents
should show up in a pop-up window containing text similar to 
"Management Center for Cisco Security Agents V4.0-1 build 540"

Details
=======

CSA versions prior to 4.0.3.728 contain a vulnerability in the buffer
overflow handling code allowing for the evasion of the protections
offered by CSA.  The evasion is timing dependent, where the second of two
closely spaced overflow attacks is not processed by CSA.

In a vulnerable release a buffer overflow will trigger the Overflow
heuristic, generating a query to the user.  This query has a countdown
timer of 5 minutes after which the default action of "Terminate" is
taken in the event that the user does not make a selection.  A second or
subsequent buffer overflow attack that is received during this countdown
period will not be trapped by CSA.

The result is that a sequence of two buffer overflow attacks in quick
succession can result in the second bypassing CSA protection.  If the
attack is targeted at a vulnerable unpatched system process privileged
access may result.

Agents prior to 4.0.3.728 are not affected if a user is not logged in
or if the hidden GUI option is in effect.  Under these circumstances the
agent knows that there is no user to respond to a query message.  Because
of this, the agent immediately takes the default action to terminate the
process thus preventing the opportunity to evade the protection provided
by CSA.

This has been documented in Cisco Bug ID CSCef96160.

Impact
======

The integrity of the system which CSA is protecting may be compromised
via privileged access which may be gained if patches for underlying
system software vulnerabilities have not been applied.

Software Versions and Fixes
===========================

Environments in which CSA is being used should ensure that they are
running version 4.0.3.728 or later with a minimum of the default desktop
or default server policy enabled.

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

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 agreement with third-party support organizations such as
Cisco Partners, authorized resellers, or service providers should
contact that support organization for assistance with the upgrade, which
should be free of charge.

Customers without Service Contracts
- -----------------------------------

Customers who purchase direct from Cisco but who do not hold a Cisco
service contract and customers who purchase through third-party vendors
but are unsuccessful at obtaining fixed software through their point
of sale 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 at cisco.com

Please have your product serial number available and 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 at cisco.com" or "security-alert at cisco.com"
for software upgrades.

See http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for
additional TAC contact information, including special localized
telephone numbers and instructions and e-mail addresses for use in
various languages.

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/public/sw-license-agreement.html,
or as otherwise set forth at Cisco.com Downloads at
http://www.cisco.com/public/sw-center/sw-usingswc.shtml.

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

Placing the agents into hidden user interface mode will cause agents
to defeat this attack technique.  This is configurable via the CSA
Management Console by selecting "No user interaction" in all applicable
groups for Microsoft Windows clients.

Exploitation and Public Announcements
=====================================

The Cisco PSIRT is aware of discussion of this vulnerability in a closed
forum.

Customers running CSA should be aware that exploits do exist which
could be used to exploit unpatched system software on machines where
vulnerable versions of CSA are running.

Status of This Notice: FINAL
============================

THIS ADVISORY IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY
KIND OF GUARANTEE OR WARRANTY. YOUR USE OF THE INFORMATION ON THE
ADVISORY OR MATERIALS LINKED FROM THE ADVISORY IS AT YOUR OWN RISK.
CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS NOTICE AT ANY TIME.

Distribution
============

This advisory is posted on Cisco's worldwide website at 
http://www.cisco.com/warp/public/707/cisco-sa-20041111-csa.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 at cisco.com
  * first-teams at first.org (includes CERT/CC)
  * bugtraq at securityfocus.com
  * vulnwatch at vulnwatch.org
  * cisco at spot.colorado.edu
  * cisco-nsp at puck.nether.net
  * full-disclosure at lists.netsys.com
  * comp.dcom.sys.cisco at 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 |                  | Initial       |
| 1.0      | 2004-November-11 | 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/.

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