An indexing error when processing the ImageDescriptor structure of GIF images can be exploited to corrupt memory via a specially crafted "ImageLeftPosition" value.
The vulnerabilities are confirmed in version 1.98.8. Other versions may also be affected
The Code
http://protekresearchlab.com/exploits/PRL-2012-18.gif
http://www.exploit-db.com/sploits/19335.gif