iDefense Security Advisory 04.08.08
http://labs.idefense.com/intelligence/vulnerabilities/ 
Apr 08, 2008

I. BACKGROUND

The HxTocCtrl ActiveX Control is a library used by the Microsoft Help
engine. More information is available at the following website.

http://en.wikipedia.org/wiki/Microsoft_Help_2 

II. DESCRIPTION

Remote exploitation of a heap corruption vulnerability in Microsoft
Corp.'s Microsoft Help 2.5 ActiveX control allows an attacker to
execute arbitrary code with the privileges of the logged-on user.

Microsoft Help 2.5 installs the following ActiveX control, which is
marked as safe for scripting:

ProgID: HxVz.HxTocCtrl.1
CLSID: 314111B8-A502-11D2-BBCA-00C04F8EC294
File: %PROGRAM DIR%\Common Files\Microsoft Shared\Help\hxvz.dll

By providing malformed arguments to this control, it is possible to
corrupt heap memory.

III. ANALYSIS

Exploitation allows attackers to execute arbitrary code with the
privileges of the logged-on user. Exploitation would require an
attacker to host a maliciously crafted page on a website and entice
users to visit that site. No further action is needed other than
following a link to a malicious website. Exploitation requires that
users have the specified control installed.

IV. DETECTION

iDefense has confirmed this vulnerability in version 2.05.50727.42 of
hxvz.dll, which is installed with Visual Studio 2005.

The following products might also include vulnerable versions of the
control:

Visual Studio 2005
Visual Studio .NET 2003
Visual Studio .NET 2002
MSDN Library 2002 - Current
BizTalk Server 2004 Standard Edition

V. WORKAROUND

Setting the kill bit for this control mitigates the threat from
web-based attacks that might be conducted via Internet Explorer. The
vulnerable CLSID is:

{314111b8-a502-11d2-bbca-00c04f8ec294}

VI. VENDOR RESPONSE

Microsoft has officially addressed this vulnerability with Security
Bulletin MS08-023. For more information, consult their bulletin at the
following URL.

http://www.microsoft.com/technet/security/bulletin/ms08-023.mspx 

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2008-1086 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org/), which standardizes names for 
security problems.

VIII. DISCLOSURE TIMELINE

12/12/2006  Initial vendor notification
12/12/2006  Initial vendor response
04/08/2008  Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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X. LEGAL NOTICES

Copyright =A9 2008 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
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