FFmpeg through 4.2 has a "Conditional jump or move depends on uninitialised value" issue in h2645_parse because alloc_rbsp_buffer in libavcodec/h2645_parse.c mishandles rbsp_buffer.
libavcodec/hevcdec.c in FFmpeg 3.4 and 4.1.2 mishandles detection of duplicate first slices, which allows remote attackers to cause a denial of service (NULL pointer dereference and out-of-array access) or possibly have unspecified other impact via crafted HEVC data.