Adobe Acrobat Reader (Unix) 5.0 Uudecode Filename Buffer Overflow Vulnerability iDEFENSE Security Advisory 08.12.04: *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 a buffer overflow in the uudecoding feature of Adobe Acrobat Reader 5.0 for Unix allows an attacker to execute arbitrary code. The Unix and Linux versions of Adobe Acrobat Reader 5.0 automatically attempt to convert uuencoded docuements back into their original format. The vulnerability specifically exists in that Acrobat Reader fails to check the length of the filename before copying it into a fixed length buffer. This allows a maliciously constructed file to cause a buffer overflow resulting in the execution of arbitrary code. *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-2004-0631 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 04/01/2004 iDEFENSE clients notified 04/06/2004 Initial vendor response 05/19/2004 Date stamp on patched binary 08/12/2004 Public disclosure *IX. CREDIT* The discoverer wishes to remain anonymous. Get paid for vulnerability research http://www.idefense.com/poi/teams/vcp.jsp *X. LEGAL NOTICES* Copyright © 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.