Heap-based buffer overflow in XnView before 1.99 allows remote attackers to cause a denial of service (application crash) and possibly execute arbitrary code via a crafted ImageLeftPosition value in an ImageDescriptor structure in a GIF image.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2012-0318
http://www.protekresearchlab.com/index.php?option=com_content&view=article&id=51
http://www.exploit-db.com/exploits/19335