The (1) AddWeightedPathSegLists and (2) SVGPathSegListSMILType::Interpolate functions in Mozilla Firefox before 42.0 and Firefox ESR 38.x before 38.4 lack status checking, which allows remote attackers to cause a denial of service (memory corruption) or possibly have unspecified other impact via a crafted SVG document.
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.