Microsoft License Manager and urlmon.dll COM Object Interaction Invalid
Memory Access Vulnerability

iDefense Security Advisory 06.12.07
http://labs.idefense.com/intelligence/vulnerabilities/
Jun 12, 2007

I. BACKGROUND

Internet Explorer is a set of core technologies in Microsoft Windows
operating systems that provide web browsing functionality. Further
information is available at URL shown below.

http://www.microsoft.com/windows/ie/default.mspx

II. DESCRIPTION

Remote exploitation of an invalid memory access vulnerability in various
Microsoft products, including Internet Explorer, while creating certain
COM objects may allow an attacker to execute arbitrary code.

When creating certain COM objects in Internet Explorer, memory
corruption can occur, which may allow an attacker to execute arbitrary
code. When calling the IObjectSafety function, uninitialized memory is
accessed in a way that can allow code execution to occur. The
IObjectSafety function is used by COM objects to determine if an object
is safe to load in a particular context.

III. ANALYSIS

Exploitation of this vulnerability could allow a remote attacker to
execute arbitrary code in the context of the currently logged in user.

One method of exploiting this vulnerability would be to craft a website
that performs the required operations. It also may be possible to embed
the controls in an Office document.

iDefense Labs successfully constructed exploit code for this
vulnerability that causes code execution, although not in a reliable
manner. It may be possible to increase the reliability using other
techniques.

IV. DETECTION

iDefense confirmed the existence of this vulnerability using Internet
Explorer 6 on Windows XP SP2 and Windows Server 2000 SP4. Although
Windows Server 2003 contains an affected version, the Enhanced Security
Configuration mitigates exposure to this vulnerability.

Microsoft reports that Internet Explorer 7 is not affected.

Other applications that can load COM objects from documents may also be
affected.

V. WORKAROUND

Setting the kill-bits for the CLSIDs associated with urlmon.dll will
prevent them from loading as ActiveX controls. While disabling the
ability to create these controls from a Web page did not appear to
cause any change in behavior, some sites or applications may exhibit
changes in functionality.

VI. VENDOR RESPONSE

Microsoft has addressed this vulnerability within MS07-033. For more
information, consult their bulletin at the following URL.

http://www.microsoft.com/technet/security/Bulletin/MS07-033.mspx

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-0218 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

10/24/2006  Initial vendor notification
01/03/2007  Initial vendor response
06/12/2007  Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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X. LEGAL NOTICES

Copyright © 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
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reliance on, this information.