Use-after-free vulnerability in the nsGenericHTMLElement::GetWidthHeightForImage function in Mozilla Firefox before 29.0, Firefox ESR 24.x before 24.5, Thunderbird before 24.5, and SeaMonkey before 2.26 allows remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via vectors involving an imgLoader object that is not properly handled during an image-resize operation.