Vulnerability Note VU#140129

Adobe Reader EScript.api arbitrary code execution

Overview

The Adobe Acrobat Reader contains a vulnerability that may allow an attacker to execute arbitrary code.

I. Description

Adobe Acrobat Reader is software designed to view Portable Document Format (PDF) files. Adobe also distributes the Adobe Acrobat Plug-In to allow users to view PDF files inside of a web browser.

Per iDefense Advisory 02.08.08:

Remote exploitation of an insecure method exposed by the JavaScript library in Adobe Reader and Acrobat could allow an attacker to execute arbitrary code as the current user.

Adobe Reader and Acrobat implement a version of JavaScript in the EScript.api plug-in which is based on the reference implementation used in Mozilla products. One of the methods exposed allows direct control over low level features of the object, which in turn allows execution of arbitrary code.

II. Impact

By convincing a user to open a malicious PDF file, a remote, unauthenticated attacker may be able to execute arbitrary code. This can happen in several ways, such as opening an email attachment or viewing a web page.

III. Solution

Update

Adobe has released Adobe Reader and Acrobat 8.1.2 to address this and other issues.

Until it is possible to upgrade to a fixed version of Adobe Acrobat, users can take the following steps to mitigate this vulnerability:

Disable the displaying of PDF documents in the web browser

Preventing PDF documents from opening inside a web browser may prevent this vulnerability from being automatically exploited. If this workaround is applied to updated versions of the Adobe reader, it may mitigate future vulnerabilities.

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

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.

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 JavaScript in Adobe Reader and Acrobat

Disabling Javascript may prevent this vulnerability from being exploited. Acrobat JavaScript can be disabled in the General preferences dialog (Edit -> Preferences -> JavaScript and un-check Enable Acrobat JavaScript).

Do not open untrusted PDF files

Do not open unfamiliar or unexpected PDF attachments. Users can convert PDF documents to text by using the Adobe Online Conversion Tools site. See the Online Conversion Tools FAQ for information about this service. This workaround will not mitigate all attack vectors.

Systems Affected

Vendor	Status	Date Updated
Adobe	Vulnerable	12-Feb-2008

References

http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=656
http://www.adobe.com/support/security/advisories/apsa08-01.html
http://www.adobe.com/products/acrobat/access_onlinetools.html
http://www.adobe.com/products/acrobat/access_tools_faq.html
http://plugindoc.mozdev.org/faqs/acroread.html

Credit

Thanks to Adobe and iDefense for information that was used in this report.

This document was written by Ryan Giobbi.

Other Information

Date Public	02/09/2008
Date First Published	02/12/2008 10:23:20 AM
Date Last Updated	02/12/2008
CERT Advisory
CVE Name	CVE-2007-5663
US-CERT Technical Alerts
Metric	12.60
Document Revision	16