CVE 2005-0399
Heap-based buffer overflow in GIF2.cpp in Firefox before 1.0.2, Mozilla before to 1.7.6, and Thunderbird before 1.0.2, and possibly other applications that use the same library, allows remote attackers to execute arbitrary code via a GIF image with a crafted Netscape extension 2 block and buffer size.
See the 
CVE page on Mitre.org
for more details.
