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.
Remote exploitation of an input validation error in the uudecoding
feature of Adobe Acrobat Reader (Unix) 5.0 allows an attacker to execute
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.
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.
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.
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.
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
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
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
Greg MacManus (iDEFENSE Labs) is credited with this discovery.
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Copyright © 2004 Verisign, Inc.
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