Vulnerability Note VU#593409

Adobe Reader and Acrobat util.printf() JavaScript function stack buffer overflow

Overview

Adobe Reader and Acrobat contain a stack buffer overflow in the util.printf() JavaScript function, which may allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system.

I. Description

Adobe Reader is software designed to view Portable Document Format (PDF) files. Adobe Acrobat is software that can create PDF files. Adobe Reader and Acrobat support JavaScript in PDF documents. According to the Acrobat Forms JavaScript Object Specification, the util.printf() function "... will format one or more values as a string according to a format string. This is similar to the C function of the same name."

Adobe Reader and Acrobat fail to sufficiently validate input to the util.printf() JavaScript function, which can result in a stack buffer overflow. Exploit code for this vulnerability is publicly available.

II. Impact

By convincing a user to open a specially-crafted 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

Apply an update

This issue is addressed in Adobe Reader and Adobe Acrobat 8.1.3. More details are available in Adobe Security Bulletin APSB08-019. Please also consider the following workarounds to help mitigate this and other vulnerabilities in Adobe Reader:

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.

Ubuntu users and administrators can prevent Adobe Reader from automatically opening PDF files inside their web browser by removing the mozilla-acroread package.

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 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	2008-05-22	2008-11-07

References

http://www.adobe.com/support/security/bulletins/apsb08-19.html
http://secunia.com/advisories/29773/
http://secunia.com/advisories/29941/
http://www.securityfocus.com/bid/30035
http://www.coresecurity.com/content/adobe-reader-buffer-overflow
http://www.milw0rm.com/exploits/9233

Credit

This vulnerability was reported by Will Dormann of the CERT/CC, based on information provided by Dyon Balding of Secunia Research.

This document was written by Will Dormann.

Other Information

Date Public	11/04/2008
Date First Published	11/04/2008 01:30:00 PM
Date Last Updated	07/23/2009
CERT Advisory
CVE Name	CVE-2008-2992
Metric	24.62
Document Revision	23

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