Use-after-free vulnerability in Mozilla Firefox before 18.0 Firefox ESR 17.x before 17.0.1 Thunderbird before 17.0.2 Thunderbird ESR 17.x before 17.0.1 and SeaMonkey before 2.15 allows remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via vectors related to Mesa drivers and a resized WebGL canvas.