Heap-based buffer overflow in Netscape 6.2.3 and Mozilla 1.0 and earlier allows remote attackers to crash client browsers and execute arbitrary code via a PNG image with large width and height values and an 8-bit or 16-bit alpha channel.
http://www.mozilla.org/releases/mozilla1.0.1/security-fixes-1.0.1.html
http://www.mandriva.com/security/advisories?name=MDKSA-2002:074