Public Vulnerability Reports

Adobe Acrobat and Reader Firefox Plugin Use After Free Vulnerability



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.


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.


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.


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.


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.


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


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 (, which standardizes names for security problems.


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


This vulnerability was reported to iDefense by Elazar Broad.

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Copyright © 2009 Verisign, Inc.

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