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
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 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.
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.
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
Greg MacManus (iDEFENSE Labs) is credited with this discovery.
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X. LEGAL NOTICES
Copyright (c) 2004 iDEFENSE, Inc.
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