iDefense Security Advisory 08.11.09: Multiple Vendor Microsoft ATL/MFC ActiveX Type Confusion Vulnerability

iDefense Security Advisory 08.11.09
http://labs.idefense.com/intelligence/vulnerabilities/
Aug 11, 2009

I. BACKGROUND

Microsoft's Component Object Model (COM) was designed to allow
interoperability between disjointed software components. It is a
standardized interface solution to the programming dilemmas involved in
object oriented programming, distributed transactions, and
inter-language communications. COM is involved at some level in DDE,
OLE, COM+, ActiveX, and DCOM. COM objects can be embedded in various
document formats, Web Pages, and various other media technologies.
Microsoft's Active Template Library (ATL) is a set of C++ templates
that simplify developing COM objects. More information on COM and ATL
can be found at the following URLs.

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

http://msdn.microsoft.com/en-us/library/t9adwcde(VS.80).aspx

II. DESCRIPTION

Remote exploitation of a type confusion vulnerability in Microsoft
Corp.'s ATL/MFC ActiveX code as included in various vendors' ActiveX
controls, could allow an attacker to execute arbitrary code within
Internet Explorer (IE).

One aspect of COM is a process called initialization. This process
allows a program to load and store a COM object within various
containers, such as OLE compound storage files and raw streams.

Depending upon certain characteristics of an OLE component designed with
certain versions of the Microsoft ATL, it is possible to cause an object
to use a variant of type VT_BSTR as a different object. In certain
circumstances, an encoded BSTR can cause ATL code to set the COM type
without checking to see if the type was successfully coerced. Upon
return, the BSTR is treated as an object leading to an attacker being
able to specify an address to call.

III. ANALYSIS

Exploitation of this vulnerability will result in the execution of
arbitrary code. Attack vectors include Internet Explorer, WordPad,
Microsoft Office, and any other program that loads arbitrary
persistence data.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability inside
Microsoft' ATL and MFC. This vulnerability appears to be limited to MFC
version 3.0. Any source code compiled with these libraries may also be
vulnerable.

V. WORKAROUND

iDefense is currently unaware of any workarounds for this issue.

VI. VENDOR RESPONSE

Microsoft has released a security bulletin which addresses this issue.
For more information, consult their advisory at the following URL:

http://www.microsoft.com/technet/security/Bulletin/MS09-037.mspx

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2009-2494 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

12/05/2008 Initial Contact
01/05/2009 Microsoft requested PoC
01/06/2009 iDefense sent PoC
01/23/2009 iDefense requested status update
01/26/2009 iDefense requested status update
01/27/2009 Microsoft reports status
02/09/2009 Microsoft reports status
02/26/2009 Microsoft reports status
03/27/2009 Microsoft reports status
04/23/2009 Microsoft reports status, predicts September release
05/13/2009 Microsoft reports status, predicts October release
05/21/2009 Microsoft requests conference call
06/03/2009 Conference call takes place
07/29/2009 Material presented at BlackHat USA
08/11/2009 Public disclosure via MS09-037

IX. CREDIT

This vulnerability was discovered by Ryan Smith of iDefense Labs.

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X. LEGAL NOTICES

Copyright © 2009 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.