Heap-based buffer overflow in the avcodec_default_get_buffer function (utils.c) in FFmpeg libavcodec 0.4.9-pre1 and earlier, as used in products such as (1) mplayer, (2) xine-lib, (3) Xmovie, and (4) GStreamer, allows remote attackers to execute arbitrary commands via small PNG images with palettes.
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.