Vulnerability Note VU#968818

Anti-virus software may not properly scan malformed zip archives

Overview

Anti-virus software may rely on corrupted headers to determine if a zip archive is valid. As a result, anti-virus software may fail to detect malicious content within a zip archive.

I. Description

Information about a zip archive, such as the size of the compressed data, is placed in headers within the archive. An attacker may be able to modify these headers to indicate that an archive contains files with sizes/lengths of zero. If anti-virus software relies on zip archive headers to determine archive validity, the anti-virus software may incorrectly interpret an archive with maliciously modified headers to contain zero-length files. Consequently, the anti-virus software would fail to detect the malicious content and allow the archive into the system.

Please note that a user may still have to extract the contents of the malicious archive to trigger exploitation.

II. Impact

A remote attacker may be able to craft a malicious zip archive that will evade detection by anti-virus software. Once in the system, if the remote attacker can persuade the user to accesses the malicious archive, the attacker may be able to execute arbitrary code on that user's system.

III. Solution

Consult Anti-Virus Vendors

Users are encouraged to contact their anti-virus vendors to determine if they are vulnerable and what corrective actions to take.

Systems Affected

Vendor	Status	Date Notified
AKS	Unknown	9-Dec-2004
Check Point	Unknown	9-Dec-2004
CommandCom	Unknown	9-Dec-2004
Computer Associates	Unknown	9-Dec-2004
CPAN	Unknown	9-Dec-2004
CyberSoft	Unknown	9-Dec-2004
eset Antivirus	Unknown	9-Dec-2004
F-Secure	Unknown	9-Dec-2004
Finjan Software	Unknown	9-Dec-2004
Fortinet	Unknown	9-Dec-2004
Kapersky	Unknown	9-Dec-2004
McAfee	Unknown	9-Dec-2004
MessageLabs	Unknown	9-Dec-2004
RAV	Unknown	9-Dec-2004
Sophos	Unknown	9-Dec-2004
Symantec Corporation	Unknown	10-Dec-2004

References

http://www.linuxsecurity.com/advisories/gentoo_advisory-5043.html
http://rt.cpan.org/NoAuth/Bug.html?id=8077
http://www.idefense.com/application/poi/display?id=153

Credit

This vulnerability was publicly reported by iDefense.

Thanks to Dan Plakosh for providing information concerning this issue.

This document was written by Jeff Gennari.

Other Information

Date Public:	2004-10-18
Date First Published:	2004-12-10
Date Last Updated:	2005-01-14
CERT Advisory:
CVE-ID(s):
NVD-ID(s):
US-CERT Technical Alerts:
Metric:	7.59
Document Revision:	106

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