Cisco Security Advisory-
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
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20041111-csa
Cisco is making patches available for CSA versions 4.0 free of charge, to correct the problem.
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This section provides details on affected products.
Vulnerable Products
The following products are affected:
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Cisco Security Agent versions up to and excluding 4.0.3 build 728
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Cisco Security Agent 3.x versions
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Okena Stormwatch 3.x versions
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Cisco Security Agent for CallManager versions up to and excluding
4.0.3 build 728
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:
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Log on to the Management console for Cisco Security Agent on your
CiscoWorks server:
http://ciscoworks-hostname:1741/
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Select VPN/Security Management Solution > Management
Center > Security Agents, and then click the Security
Agents tab.
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
Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by these vulnerabilities.
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Cisco Security Agent versions up to and excluding 4.0.3 build 728
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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 (registered customers only).
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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.
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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.
Customers running Cisco Security Agent for CallManager should ensure that they are running version CiscoCM-CSA-4.0.3.728-1.1.9 or later.
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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.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Revision 1.2
2004-December-1
Corrected URL in Summary section.
Revision 1.1
2004-November-19
Updated affected products and fixed software to include CSA agent fix on Cisco CallManager.
Revision 1.0
2004-November-11
Initial public release.
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