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Adobe Reader and Acrobat XSLT utf8ToUtf16() Heap Overflow Vulnerability



Adobe Acrobat and Adobe Reader are portable document format (PDF) processors and readers, respectively.

For more information, please visit the following pages:


Remote exploitation of a heap overflow vulnerability in Adobe Systems Inc.'s Reader could allow an attacker to execute arbitrary code with the privileges of the current user.

The vulnerability is in Adobe Reader's Extensible Stylesheet Language Transformations (XSLT) engine during the parsing of UTF-8 strings in an XSL file embedded within a PDF file. The utf8ToUtf16() function is used to convert strings. When invalid UTF-8 characters are provided, this function will write after the requested buffer and lead to a heap buffer overflow condition. This can result in the execution of arbitrary code.


Exploitation of this vulnerability results in the execution of arbitrary code with the privileges of the user viewing a Web page or opening a PDF file. Since PDF files can be embedded into Web pages and parsed without interaction by default, this vulnerability can be exploited as a typical browser vulnerability. To exploit this vulnerability, a targeted user must load a malicious Web page that an attacker created. An attacker typically accomplishes this via social engineering or injecting content into compromised, trusted sites. After the user visits the malicious Web page, no further user interaction is needed.


Adobe Acrobat and Reader X for Windows and Macintosh prior to version 10.1.4 are vulnerable. Adobe Reader and Acrobat for Windows and Macintosh versions prior to 9.5.2 are also vulnerable.


None of the following workarounds will prevent exploitation, but they can reduce the number of potential attack vectors and make exploitation more difficult:

  • Prevent PDF documents from being opened automatically by Web browsers
  • Disable JavaScript
  • Disable the PDFShell extension by removing or renaming the Acrord32info.exe file
  • Use the Microsoft EMET tool to run Adobe Acrobat and Reader
  • Upgrade to Adobe Acrobat and Reader X
  • Follow best practice methodologies by avoiding opening files from untrusted or unsolicited sources


Adobe Systems Inc. has released patches which address this issue. For more information, consult their advisory at the following URL:


The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2012-1525 to this issue. This is a candidate for inclusion in the CVE list (, which standardizes names for security problems.


05/02/2012 Initial Vendor Notification
05/02/2012 Initial Vendor Reply
08/14/2012 Coordinated Public Disclosure


This vulnerability was reported to iDefense by Nicolas Grégoire.

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Copyright © 2012 Verisign, 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.