Adobe Reader and Acrobat JavaScript Vulnerabilities

Original release date: May 13, 2009
Last revised: --
Source: US-CERT

Systems Affected

• Adobe Reader versions 9.1, 8.1.4, 7.1.1 and earlier
• Adobe Acrobat Standard, Pro, and Pro Extended versions 9.1, 8.1.4, 7.1.1 and earlier

Overview

Adobe has released Security Bulletin APSB09-06, which describes Adobe Reader and Acrobat updates for two JavaScript vulnerabilities that could allow a remote attacker to execute arbitrary code.

I. Description

Adobe Security Bulletin APSB09-06 announces updates for two JavaScript vulnerabilities that affect Adobe Reader and Acrobat.

• A vulnerability in the getAnnots() method (CVE-2009-1492) affects Adobe Reader and Acrobat for Microsoft Windows, Apple Mac OS X, and UNIX.
• A vulnerability in the customDictionaryOpen() method (CVE-2009-1493) appears to only affect Adobe Reader for UNIX.

Further details are available in Vulnerability Note VU#970180.

An attacker could exploit these vulnerabilities by convincing a user to open a specially crafted Adobe Portable Document Format (PDF) file. Acrobat integrates with popular web browsers, and visiting a website is usually sufficient to cause Reader or Acrobat to open a PDF file.

II. Impact

By convincing a victim to open a specially crafted PDF file, a remote, unauthenticated attacker may be able to execute arbitrary code.

III. Solution

Update

Adobe has released updates to address this issue. Users are encouraged to read Adobe Security Bulletin APSB09-06 and update vulnerable versions of Adobe Reader and Acrobat. According to APSB09-06, these vulnerabilities are addressed in versions 9.1.1, 8.1.5, and 7.1.2 of Adobe Reader and Acrobat.

Disable JavaScript in Adobe Reader and Acrobat

Disabling JavaScript prevents these vulnerabilities from being exploited and reduces attack surface. If this workaround is applied to updated versions of the Adobe Reader and Acrobat, it may protect against future vulnerabilities.

To disable JavaScript in Adobe Reader:

1. Open Adobe Acrobat Reader.
2. Open the Edit menu.
3. Choose the Preferences... option.
4. Choose the JavaScript section.
5. Uncheck the Enable Acrobat JavaScript check box.

Disabling JavaScript will not resolve the vulnerabilities, it will only disable the vulnerable JavaScript component. When JavaScript is disabled, Adobe Reader and Acrobat prompt to re-enable JavaScript when opening a PDF that contains JavaScript.

Prevent Internet Explorer from automatically opening PDF documents

The installer for Adobe Reader and Acrobat configures Internet Explorer to automatically open PDF files without any user interaction. This behavior can be reverted to the safer option of prompting the user by importing the following as a .REG file:

Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\AcroExch.Document.7]
"EditFlags"=hex:00,00,00,00

Disable the display of PDF documents in the web browser

Preventing PDF documents from opening inside a web browser reduces attack surface. If this workaround is applied to updated versions of the Adobe Reader and Acrobat, it may protect against future vulnerabilities.

To prevent PDF documents from automatically being opened in a web browser with Adobe Reader:

1. Open Adobe Acrobat Reader.
2. Open the Edit menu.
3. Choose the preferences option.
4. Choose the Internet section.

Un-check the "Display PDF in browser" check box.

Rename or remove Annots.api

To disable the vulnerable getAnnots() method, rename or remove the Annots.api file. This will disable some Annotation functionality, however annotations can still be viewed. This does not protect against the customDictionaryOpen() vulnerability.

On Windows, Annots.api is typically located here:

"%ProgramFiles%\Adobe\Reader 9.0\Reader\plug_ins"

Example location on GNU/Linux:

       /opt/Adobe/Reader8/Reader/intellinux/plug_ins/Annots.api

Do not access PDF documents from untrusted sources

Do not open unfamiliar or unexpected PDF documents, particularly those hosted on web sites or delivered as email attachments. Please see Cyber Security Tip ST04-010.

IV. References

• Vulnerability Note VU#970180 - <http://www.kb.cert.org/vuls/id/970180>
• Cyber Security Tip ST04-010: Using Caution with Email Attachments - <http://www.us-cert.gov/cas/tips/ST04-010.html>
• Adobe Security Bulletin APSB09-06 - <http://www.adobe.com/support/security/bulletins/apsb09-06.html>
• CVE-2009-1492 - <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-1492>
• CVE-2009-1493 - <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-1493>

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Feedback can be directed to US-CERT.

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Revision History

May 13, 2009: Initial release