‘Adobe Reader and Acrobat FlateDecode Integer Overflow Vulnerability’

Summary

Remote exploitation of an integer overflow vulnerability in multiple versions of Adobe Systems Inc’s Reader and Acrobat PDF reader and processor could allow an attacker to execute arbitrary code with the privileges of the current user.’

Credit:

‘The information has been provided by Jun Mao and Ryan Smith.
The original article can be found at: http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=807


Details

Vulnerable Systems:
 * Acrobat Reader versions 9.0.0 and prior
 * Acrobat Professional versions 9.0.0 and prior

The vulnerability occurs when parsing a FlateDecode filter inside a PDF file. FlateDecode is a filter for data compressed with zlib deflate compression method. Several parameters can be specified for the FlateDecode filter. Those values are used in an arithmetic operation that calculates the number of bytes to allocate for a heap buffer. This calculation can overflow, which results in an undersized heap buffer being allocated. This buffer is then overflowed with data decompressed from the FlateDecode stream. This leads to a heap-based buffer overflow that can result in arbitrary code execution.

Exploitation of this vulnerability allows the attacker to execute arbitrary code with the privileges of the user opening the file. The attacker will have to create a malicious PDF file and convince the victim to open it. This can be accomplished by embedding the PDF file into an IFRAME inside of a Web page, which will result in automatic exploitation once the page is viewed. The file could also be e-mailed as an attachment or placed on a file share. In these cases, a user would have to manually open the file to trigger exploitation. If preview is enable in Windows Explorer, this vulnerability can be triggered simply by accessing a folder containing PDF files.

Patch Availability:
Adobe has released a patch which addresses this issue. For more information, consult their advisory (APSB09-07) at the following URL:
http://www.adobe.com/support/security/bulletins/apsb09-07.html

CVE Information:
CVE-2009-1856

Workarounds:
None of the following workarounds will prevent exploitation, but they can reduce potential attack vectors and make exploitation more difficult.
 * Prevent PDF documents from being opened automatically by the Web browser
 * Disable JavaScript
 * Disable PDFShell extention by removing or renaming Acrord32info.exe file.
 * Follow best practice methodologies by avoiding opening files from untrusted or unsolicited sources
 * Deploy DEP (Data Execution Prevention)

Patch Availability:
Adobe has released a patch which addresses this issue. For more information, consult their advisory (APSB09-07) at the following URL:
http://www.adobe.com/support/security/bulletins/apsb09-07.html

Disclosure Timeline:
02/25/2009 – Initial Contact
02/25/2009 – Initial Response
02/25/2009 – PoC Requested
02/25/2009 – PoC Sent
06/05/2009 – Tentative disclosure date of 06/09/2009 set
06/09/2009 – Coordinated public disclosure’

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