Adobe Photoshop 12.0 in Creative Suite 5 (CS5) and 12.1 in Creative Suite 5.1 (CS5.1) allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted GIF file.
http://www.us-cert.gov/cas/techalerts/TA11-222A.html
http://www.adobe.com/support/security/bulletins/apsb11-22.html