I. Description

Adobe Security Bulletin APSB09-01 describes a memory-corruption vulnerability that affects Adobe Reader and Acrobat. Further details are available in Vulnerability Note VU#905281.

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

II. Impact

An attacker may be able to execute arbitrary code.

III. Solution

Disable JavaScript in Adobe Reader and Acrobat

Disabling Javascript may prevent some exploits from resulting in code execution. Acrobat JavaScript can be disabled using the Preferences menu (Edit -> Preferences -> JavaScript and un-check Enable Acrobat 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_ROOTAcroExch.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 will partially mitigate this vulnerability. If this workaround is applied it may also mitigate future vulnerabilities.

To prevent PDF documents from automatically being opened in a web browser, do the following:

1. Open Adobe Acrobat Reader.
2. Open the Edit menu.
3. Choose the preferences option.
4. Choose the Internet section.
5. Un-check the "Display PDF in browser" check box.

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

• Adobe Security Bulletin apsa09-01 - http://www.adobe.com/support/security/advisories/apsa09-01.html>
• Securing Your Web Browser - http://www.us-cert.gov/reading_room/securing_browser/>
• Vulnerability Note VU#905281 - http://www.kb.cert.org/vuls/id/905281>