Vulnerability Note VU#264729

Adobe Reader and Acrobat font memory corruption vulnerability

Original Release date: 15 Jun 2011 | Last revised: 28 Mar 2012

Overview

Adobe Reader and Acrobat fail to properly handle font data, which could allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system.

Description

A critical vulnerability exists in the font parsing code in Adobe Reader and Acrobat. The vulnerability results in memory corruption, which could allow for the execution of arbitrary code.

Impact

An attacker may use a specifically crafted PDF document to cause a crash or execute arbitrary code.

Solution

Apply an update

Adobe recommends all users upgrade to Adobe Reader and Acrobat 10.1, 9.4.5, or 8.3. APSB11-16 contains more details. Please also consider the following workarounds:

Use the Microsoft Enhanced Mitigation Experience Toolkit

The Microsoft Enhanced Mitigation Experience Toolkit (EMET) can be used to help prevent exploitation of this and other vulnerabilities.

Enable DEP in Microsoft Windows

Consider enabling Data Execution Prevention (DEP) in supported versions of Windows. DEP should not be treated as a complete workaround, but it can mitigate the execution of attacker-supplied code in some cases. Microsoft has published detailed technical information about DEP in Security Research & Defense blog posts "Understanding DEP as a mitigation technology" part 1 and part 2. DEP should be used in conjunction with the application of patches or other mitigations described in this document.

Note that when relying on DEP for exploit mitigation, it is important to use a system that supports Address Space Layout Randomization (ASLR) as well. ASLR is not supported by Windows XP or Windows Server 2003 or earlier. ASLR was introduced with Microsoft Windows Vista and Windows Server 2008. Please see the Microsoft SRD blog entry: On the effectiveness of DEP and ASLR for more details.

Disable JavaScript in Adobe Reader and Acrobat

Disabling JavaScript helps to reduce attack surface and mitigates some exploitation techniques. If this workaround is applied to updated versions of 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 checkbox.
Note that 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 displaying 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 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.
  5. Uncheck the Display PDF in browser checkbox.

Vendor Information (Learn More)

VendorStatusDate NotifiedDate Updated
AdobeAffected29 Nov 201015 Jun 2011
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base 9.0 AV:N/AC:M/Au:N/C:C/I:C/A:P
Temporal 7.0 E:POC/RL:OF/RC:C
Environmental 7.0 CDP:ND/TD:ND/CR:ND/IR:ND/AR:ND

References

Credit

This vulnerability was reported by Will Dormann of the CERT/CC.

This document was written by Will Dormann.

Other Information

  • CVE IDs: CVE-2011-2105
  • Date Public: 14 Jun 2011
  • Date First Published: 15 Jun 2011
  • Date Last Updated: 28 Mar 2012
  • Severity Metric: 21.87
  • Document Revision: 13

Feedback

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