In FFmpeg 4.0.1, a missing check for failure of a call to init_get_bits8() in the avpriv_ac3_parse_header function in libavcodec/ac3_parser.c may trigger a NULL pointer dereference while converting a crafted AVI file to MPEG4, leading to a denial of service.
https://github.com/FFmpeg/FFmpeg/commit/00e8181bd97c834fe60751b0c511d4bb97875f78