Netscape 6.2.3 and earlier, and Mozilla 1.0.1, allow remote attackers to corrupt heap memory and execute arbitrary code via a GIF image with a zero width.
http://www.redhat.com/support/errata/RHSA-2003-046.html
http://www.redhat.com/support/errata/RHSA-2002-192.html
http://www.mandrakesoft.com/security/advisories?name=MDKSA-2002:075
http://www.iss.net/security_center/static/10058.php
http://marc.info/?l=bugtraq&m=103134051120770&w=2