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ESB-2007.0537 -- [Win] -- Trillian Instant Messenger client fails to properly handle malformed URIs

Date: 20 July 2007
References: ESB-2007.0613  

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             AUSCERT External Security Bulletin Redistribution

                          ESB-2007.0537 -- [Win]
 Trillian Instant Messenger client fails to properly handle malformed URIs
                               20 July 2007

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

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:              Trillian Instant Messenger
Publisher:            US-CERT
Operating System:     Windows
Impact:               Execute Arbitrary Code/Commands
Access:               Remote/Unauthenticated
CVE Names:            CVE-2007-3832 CVE-2007-3833

Original Bulletin:    http://www.kb.cert.org/vuls/id/786920

Revision History:     July 20 2007: Updated to reflect US-CERT update
                      July 19 2007: Added CVE Number
                      July 18 2007: Initial Release

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Vulnerability Note VU#786920

Trillian Instant Messenger client fails to properly handle malformed URIs

Overview

   The Trillian Instant Messaging client contains a buffer overflow
   vulnerability that may allow an attacker to execute code.

I. Description

   A Uniform Resource Identifier (URI) is a string of characters that can
   be used to identify a location, resource, or protocol. The Trillian
   Instant Messenger client is an IM application that supports multiple
   services, including AOL Instant Messenger. Trillian registers itself
   as the default handler for aim: URIs during installation. Web browsers
   may pass URIs to other applications that have been registered to
   handle them.

   A buffer overflow vulnerability exists in the Trillian Instant
   Messenger client. An attacker may exploit this vulnerability by
   convincing a user to open a malformed aim: URI inside of a web
   browser. When the web browser passes the malformed URI to the Trillian
   Instant Messenger client, the overflow may be triggered.
   Note that some web browsers may present a dialog box warning that the
   aim: URI is being handed off to another program.

II. Impact

   A remote, unauthenticated attacker may be able to execute arbitrary
   code with the privileges of the user running Trillian.

III. Solution

   We are currently unaware of a practical solution to this problem.

   Unregister the AIM protocols
   Disabling the AIM protocol handler can mitigate this vulnerability. To
   unregister the protocol handler, delete or rename the following
   registry key:
   HKEY_CLASSES_ROOT\AIM\
   Note that when Trillian (trillian.exe) is started, it will attempt to
   recreate or repair the registry key. On Windows XP SP2 by default,
   Administrators and Power Users have permissions to modify the registry
   key. To prevent Trillian from recreating the registry key, run
   Trillian with a limited user account. Alternatively, change or delete
   the value for
   HKEY_CLASSES_ROOT\AIM\shell\open\command
   and [21]change permissions so that the appropriate user groups can not
   recreate or repair the key.
   Block access to aim: URIs
   Administrators may partially mitigate this vulnerability by blocking
   access to the aim: URI using proxy server access control lists or the
   appropriate content filtering rule.

Systems Affected

   Vendor                   Status         Date Updated
   America Online, Inc. Not Vulnerable 16-Jul-2007
   http://www.kb.cert.org/vuls/id/RGII-756S8E
   Cerulean Studios     Vulnerable     16-Jul-2007
   http://www.kb.cert.org/vuls/id/RGII-756RFW

References

   http://www.xs-sniper.com/nmcfeters/Cross-App-Scripting-2.html
   http://en.wikipedia.org/wiki/Uniform_Resource_Identifier
   http://secunia.com/advisories/26086/
   http://technet2.microsoft.com/windowsserver/en/library/2621d47b-714b-4549-8f21-29ea082ed76b1033.mspx?mfr=true

Credit

   This issue was disclosed by Nate Mcfeters, Billy (BK) Rios, Raghav
   "the Pope" Dube.

   This document was written by Ryan Giobbi.

Other Information

            Date Public 07/15/2007
   Date First Published 07/16/2007 04:40:45 PM
      Date Last Updated 07/18/2007
          CERT Advisory
               CVE Name
                 Metric 23.76
      Document Revision 25


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===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
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