Use-after-free vulnerability in the nsTArray_base::Length function in Mozilla Firefox before 15.0 Firefox ESR 10.x before 10.0.7 Thunderbird before 15.0 Thunderbird ESR 10.x before 10.0.7 and SeaMonkey before 2.12 allows remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via vectors involving movement of a requiredFeatures attribute from one SVG document to another.