iDefense Security Advisory 10.13.09
http://labs.idefense.com/intelligence/vulnerabilities/
Oct 13, 2009

I. BACKGROUND

Adobe Acrobat Reader/Acrobat are programs for viewing and editing
Portable Document Format (PDF) documents. For more information, see the
vendor's site found at the following link.

http://www.adobe.com/products/reader/
http://www.adobe.com/products/acrobatpro/

II. DESCRIPTION

Remote exploitation of a use after free vulnerability in Adobe Systems
Inc.'s Acrobat and Reader Firefox plugin could allow an attacker to
execute arbitrary code with the privileges of the current user.

When Adobe Acrobat/Reader is installed, it also installs various browser
plugins that allow PDF documents to be viewed in the browser. This
vulnerability occurs within the Firefox browser plugin. The Internet
Explorer version is not affected.

The vulnerability occurs when Firefox attempts to navigate away from a
page and unload the PDF viewing plugin. When Firefox calls the plugin's
destroy method, the plugin does not properly free its resources.
Specifically, a function pointer for the window update routine is not
properly freed. This results in uninitialized memory being used when
the window is redrawn, which leads to attacker supplied data being
executed when the function pointer is dereferenced.

III. ANALYSIS

Exploitation of this vulnerability results in the execution of arbitrary
code with the privileges of the user viewing the web page. In order to
exploit this vulnerability, the plugin must be enabled, and the
"Display PDF in browser" option must be checked. Both of these are
default settings.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in Acrobat
and Reader versions 8.1.3, 8.1.4, 8.1.5, and 8.1.6. Previous versions
are also likely affected. Version 9.1.3 and previous 9.x versions are
not affected.

V. WORKAROUND

Disabling the Adobe Firefox plugin will prevent the exploitation of this
vulnerability. However, it will also prevent a user from viewing PDFs
within the browser.

Disabling JavaScript in the browser and in Adobe Acrobat/Reader will
increase the difficulty of successfully exploiting this vulnerability,
but it will not prevent it from triggering.

VI. VENDOR RESPONSE

Adobe has addressed this issue with an update. Further details and
patches can be found at the following URL.

http://www.adobe.com/support/security/bulletins/apsb09-15.html

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2009-2991 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

06/22/2009  Initial vendor notification
06/22/2009  Initial vendor response
10/13/2009  Coordinated Public disclosure

IX. CREDIT

This vulnerability was reported to iDefense by Elazar Broad.

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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
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