[NT] Microsoft Windows 2000 Agent URL Canonicalizing Stack Based Buffer Overflow Vulnerability

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Microsoft Windows 2000 Agent URL Canonicalizing Stack Based Buffer
Overflow Vulnerability
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SUMMARY

<http://www.microsoft.com/msagent/default.asp> Microsoft Agent allows
"websites and programs to display animated characters that speak and move
around the screen. The Microsoft Office "Clippy" character, the animated
paper clip, is an example of a Microsoft agent character. Agents can be
created through the web browser by loading and interacting with an ActiveX
control. Once this control is loaded it will start the Agent Service
process, and pass requests from the browser to the service".

Remote exploitation of a stack based buffer overflow vulnerability in
Microsoft Corp's Microsoft Windows 2000 Agent service could allow an
attacker to execute arbitrary code with the privileges of the logged in
user.

DETAILS

Vulnerable Systems:
* iDefense has confirmed the existence of this vulnerability in the Agent
service included in Windows 2000.

Immune Systems:
* Microsoft reports that newer versions of the Agent service are not
vulnerable.

The vulnerability exists within the Agent Service (agentsvr.exe). Due to
improper handling of specially crafted URLs, an attack can cause stack
based buffer overflow.

Exploitation of this vulnerability results in arbitrary code execution
with the privileges of the logged in user. To exploit this vulnerability,
an attacker would have to use social engineering techniques to convince a
user to visit a malicious website. No further interaction is needed.

With default settings, Microsoft Outlook and Outlook Express can not be
used to directly exploit this vulnerability. By default, Outlook and
Outlook Express both run in Restricted mode which prevents Active Content
from being loaded. However, an attacker could send an e-mail with a link
to a malicious website. By following this link a user is susceptible to
exploitation through the browser.

Workaround:
Setting the kill bit for the following CLSID will prevent the control from
loading in the browser:
{D45FD31B-5C6E-11D1-9EC1-00C04FD7081F}

This will not fix the vulnerability, but it will prevent it from being
exploited through the web browser.

Vendor Status:
Microsoft has addressed this vulnerability within MS07-051. For more
information, consult their bulletin at the following URL.
<http://www.microsoft.com/technet/security/Bulletin/MS07-051.mspx>
http://www.microsoft.com/technet/security/Bulletin/MS07-051.mspx

CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-3040>
CVE-2007-3040

Disclosure Timeline:
* 07/09/2007 Initial vendor notification
* 07/09/2007 Initial vendor response
* 09/11/2007 Coordinated public disclosure


ADDITIONAL INFORMATION

The information has been provided by iDefense.
The original article can be found at:

<http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=592>
http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=592



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