Vulnerability Note VU#905281

Adobe Reader and Acrobat JBIG2 buffer overflow vulnerability

Overview

Adobe Reader and Acrobat contain a buffer overflow 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. Adobe Reader and Acrobat contain a buffer overflow vulnerability in the handling of JBIG2 streams.

Exploit code for this vulnerability is publicly available.

II. Impact

By convincing a user to open a malicious PDF file, an attacker may be able to execute code or cause a vulnerable PDF viewer to crash. The PDF could be emailed as an attachment or hosted on a website.

III. Solution

Apply an update

This issue is addressed in Adobe Reader and Acrobat versions 9.1, 8.1.4, and 7.1.1. More details are available in Adobe Security Bulletin APSB09-03 and APSB09-04.

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). Note that this will not block the vulnerability. Adobe products still may crash when parsing specially crafted PDF documents. Disabling JavaScript will mitigate a common method used to achieve code execution with this vulnerability. Also note that when JavaScript is disabled in Adobe Reader, the software will prompt the user to enable JavaScript when it opens a document that uses the feature. So although JavaScript is a single click away, setting this preference can help mitigate exploits that use JavaScript. Some have reported that they have successfully achieved code execution without the use of JavaScript.

Some vendors ship JavaScript support in a separate package. Removing this package may remove JavaScript support in the Adobe PDF reader.

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 may mitigate this vulnerability. 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:

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

Disable Adobe Acrobat Windows Shell integration

Adobe Acrobat and Reader integrates itself with the Windows shell. The file pdfshell.dll is used to configure Windows Explorer to launch Adobe components to render, preview, and obtain details from a PDF document, all without actually opening the PDF document itself. Windows Shell integration for Adobe Acrobat and Reader can be disabled by unregistering the pdfshell.dll by running the following command:

regsvr32 /u "%CommonProgramFiles%\Adobe\Acrobat\ActiveX\pdfshell.dll"

Disable the Adobe Acrobat Indexing Service filter

Adobe Reader and Adobe Acrobat install an Indexing Service filter that is used to parse PDF files. These filters are provided by AcroRdIF.dll and AcroIF.dll, respectively. When an application that uses the Adobe IFilters indexes a malicious PDF document, the vulnerability may be triggered. This attack vector can be mitigated by unregistering the Adobe IFilter files.
Adobe Acrobat users should locate the Acrobat directory and run: regsvr32 /u AcroIF.dll
Adobe Reader users should locate the Adobe Reader directory and run: regsvr32 /u AcroRdIF.dll

Note: After disabling the Windows shell integration or the Indexing Service filter by unregistering the appropriate DLL, the Windows Installer MSI resiliency feature may trigger a "repair" of those features when an advertised shortcut for Adobe Reader is clicked. To prevent this from occurring, delete the Adobe Reader icon from the Windows start menu and then re-create a normal, non-advertised shortcut. More details are available in the CERT/CC Vulnerability Analysis Blog.

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.

Systems Affected

Vendor	Status	Date Notified	Date Updated
Adobe	Vulnerable	2009-02-19	2009-03-11

References

http://www.us-cert.gov/cas/tips/ST04-010.html
http://www.cert.org/tech_tips/securing_browser/
http://www.cert.org/blogs/vuls/2009/03/windows_installer_application.html
http://www.adobe.com/support/security/advisories/apsa09-01.html
http://www.adobe.com/support/security/bulletins/apsb09-03.html
http://www.avertlabs.com/research/blog/index.php/2009/02/19/new-backdoor-attacks-using-pdf-documents/
http://jbig2.com/
http://www.shadowserver.org/wiki/pmwiki.php?n=Calendar.20090219
http://www.shadowserver.org/wiki/pmwiki.php?n=Calendar.20090221
http://vrt-sourcefire.blogspot.com/2009/02/homebrew-patch-for-adobe-acroreader-9.html
http://secunia.com/blog/44/
http://www.milw0rm.com/exploits/8090

Credit

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

This document was written by Will Dormann and Ryan Giobbi.

Other Information

Date Public:	2009-02-19
Date First Published:	2009-02-20
Date Last Updated:	2009-03-18
CERT Advisory:
CVE-ID(s):	CVE-2009-0658
NVD-ID(s):	CVE-2009-0658
US-CERT Technical Alerts:
Metric:	32.91
Document Revision:	95

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Produced 2009 by US-CERT, a government organization
Disclaimers and copyright information

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