[Full-Disclosure] iDEFENSE Security Advisory 08.12.04a: Adobe Acrobat Reader (Unix) Shell Metacharacter Code Execution Vulnerability

2004-08-17T00:00:00
ID SECURITYVULNS:DOC:6612
Type securityvulns
Reporter Securityvulns
Modified 2004-08-17T00:00:00

Description

Adobe Acrobat Reader (Unix) Shell Metacharacter Code Execution Vulnerability

iDEFENSE Security Advisory 08.12.04a www.idefense.com/application/poi/display?id=124&type=vulnerabilities August 12, 2004

I. BACKGROUND

Adobe Acrobat Reader is a program for viewing Portable Document Format (PDF) documents. Uuencoding is a scheme that converts 8 bit data into a 6 bit format, suitable for transmission via e-mail.

II. DESCRIPTION

Remote exploitation of an input validation error in the uudecoding feature of Adobe Acrobat Reader (Unix) 5.0 allows an attacker to execute arbitrary code.

The Unix and Linux versions of Adobe Acrobat Reader 5.0 automatically attempt to convert uuencoded documents back into their original format. The vulnerability specifically exists in the failure of Acrobat Reader to check for the backtick shell metacharacter in the filename before executing a command with a shell. This allows a maliciously constructed filename to execute arbitrary programs.

III. ANALYSIS

Successful exploitation allows attackers to execute arbitrary code under the privileges of the user who opened the malicious document with a vulnerable version of Adobe Acrobat Reader. PDF documents are frequently exchanged via e-mail and in combination with a social engineering attack allows attackers to remotely exploit this vulnerability.

IV. DETECTION

Adobe Acrobat Reader (Unix) versions 5.05 and 5.06 have been confirmed vulnerable; earlier versions that call the uudecode utility are also thought to be vulnerable.

V. WORKAROUNDS

Users must be wary when opening attachments from untrusted sources whether they are executable or not. As the Windows version of Acrobat Reader is not vulnerable to the described vulnerability it can be safely used to open PDF documents suspected to be maliciously designed to exploit this issue.

VI. VENDOR RESPONSE

iDEFENSE brought this vulnerability to the attention of the vendor according to the publicized timeline. However, the vendor appears to have silently fixed this vulnerability without coordinating public disclosure of the issue. Moreover, the vendor does not appear to have publicly posted details of the security fix to inform clients of the risks posed by unpatched versions of the software. While it is not clear exactly when the vulnerability was patched, iDEFENSE has tested Adobe Acrobat Reader (UNIX) 5.0.9, which appears to be patched against this vulnerability.

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CAN-2004-0630 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems.

VIII. DISCLOSURE TIMELINE

03/30/2004 Initial vendor notification 04/05/2004 iDEFENSE clients notified 04/06/2004 Initial vendor response 05/19/2004 Date stamp on patched binary 08/12/2004 Public disclosure

IX. CREDIT

Greg MacManus (iDEFENSE Labs) is credited with this discovery.

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X. LEGAL NOTICES

Copyright (c) 2004 iDEFENSE, Inc.

Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDEFENSE. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please email customerservice@idefense.com for permission.

Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.


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