VeriSign ConfigChk ActiveX Control Buffer Overflow Vulnerability

iDefense Security Advisory 02.22.07
http://labs.idefense.com/intelligence/vulnerabilities/ 
Feb 22, 2007

I. BACKGROUND

The ConfigChk ActiveX Control is part of VeriSign Inc.'s MPKI, Secure
Messaging for Microsoft Exchange and Go Secure! products. It looks for the
Microsoft Enhanced Cryptographic Provider in order to support 1024-bit
cryptography.

II. DESCRIPTION

Remote exploitation of a buffer overflow vulnerability in VeriSign Inc.'s
ConfigChk ActiveX Control could allow an attacker to execute arbitrary
code within the security context of the victim.

The ActiveX control in question, identified by CLSID
08F04139-8DFC-11D2-80E9-006008B066EE, is marked as being safe for
scripting.

The vulnerability specifically exists when processing lengthy parameters
passed to the VerCompare() method. If either of the two parameters passed
to this method are longer than 28 bytes, stack memory corruption will
occur. This amounts to a trivially exploitable stack-based buffer
overflow.

III. ANALYSIS

Successful exploitation of this vulnerability would allow a remote attacker
to execute arbitrary code within the context of the victim.

In order to exploit this vulnerability, an attacker would need to persuade
the victim into viewing a malicious web site. This is usually accomplished
by getting the victim into clicking a link in a form of electronic
communication such as e-mail or instant messaging.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability within version
2.0.0.2 of VeriSign Inc's VSCnfChk.dll. All versions are suspected to be
vulnerable.

V. WORKAROUND

Setting the kill-bit for this control will prevent exploitation of this
vulnerability through Internet Explorer.

VI. VENDOR RESPONSE

VeriSign has addressed this vulnerability by releasing a patch which
corrects the security issues found in the affected .dll file.

VII. CVE INFORMATION

A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.

VIII. DISCLOSURE TIMELINE

12/22/2006  Initial vendor notification
12/20/2006  Initial vendor response
02/22/2007  Coordinated public disclosure

IX. CREDIT

This vulnerability was discovered by David D. Rude II (iDefense).

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X. LEGAL NOTICES

Copyright =A9 2007 iDefense, Inc.

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Disclaimer: The information in the advisory is believed to be accurate at
the time of publishing based on currently available information. Use of
the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on, this
information.