vmtypedarrayobject.cpp in Mozilla Firefox before 28.0, Firefox ESR 24.x before 24.4, Thunderbird before 24.4, and SeaMonkey before 2.25 does not validate the length of the destination array before a copy operation, which allows remote attackers to execute arbitrary code or cause a denial of service (out-of-bounds write and application crash) by triggering incorrect use of the TypedArrayObject class.