The libxul.so!gfxContext::Polygon function in Mozilla Firefox before 28.0, Firefox ESR 24.x before 24.4, Thunderbird before 24.4, and SeaMonkey before 2.25 allows remote attackers to obtain sensitive information from process memory, cause a denial of service (out-of-bounds read and application crash), or possibly bypass the Same Origin Policy via vectors involving MathML polygon rendering.
The product reads data past the end, or before the beginning, of the intended buffer.