The decode_uncompressed function in libavcodec/faxcompr.c in FFmpeg before 2.8.2 does not validate uncompressed runs, which allows remote attackers to cause a denial of service (out-of-bounds array access) or possibly have unspecified other impact via crafted CCITT FAX data.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.