The decode_mb function in libavcodec/error_resilience.c in FFmpeg before 0.10 allows remote attackers to have an unspecified impact via vectors related to an uninitialized block index, which triggers an out-of-bounds write.
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.