The sbr_qmf_synthesis function in libavcodec/aacsbr.c in FFmpeg before 0.9.1 allows remote attackers to cause a denial of service (application crash) via a crafted mpg file that triggers memory corruption involving the v_off variable, probably a buffer underflow.
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.