Public Vulnerability Reports

Adobe Acrobat Reader (Unix) 5.0 Uudecode Filename Buffer Overflow Vulnerability

08.12.04

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.

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.

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.

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.

WORKAROUND

S

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.

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.

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.

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

CREDIT

The discoverer wishes to remain anonymous.

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LEGAL NOTICES

Copyright © 2004 Verisign, 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.