The mozilla::AudioSink function in Mozilla Firefox before 40.0 and Firefox ESR 38.x before 38.2 mishandles inconsistent sample formats within MP3 audio data, which allows remote attackers to execute arbitrary code or cause a denial of service (out-of-bounds read) via a malformed file.
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.