CVE 2013-0768
Stack-based buffer overflow in the Canvas implementation in Mozilla Firefox before 18.0, Firefox ESR 17.x before 17.0.2, Thunderbird before 17.0.2, Thunderbird ESR 17.x before 17.0.2, and SeaMonkey before 2.15 allows remote attackers to execute arbitrary code via an HTML document that specifies invalid width and height values.
See the 
CVE page on Mitre.org
for more details.
