FFmpeg 4.4 - 8.1.2 Double-Free in NVDEC Hardware Decoder via nvdec.c

FFmpeg versions 4.4 through 8.1.2 contain a double-free vulnerability in the NVIDIA NVDEC hardware decoder within libavcodec/nvdec.c that allows attackers to trigger memory corruption by supplying a crafted video file. When no decoder surfaces remain, the ff_nvdec_start_frame_sep_ref error path frees memory via nvdec_fdd_priv_free while the calling layer subsequently frees the same frame description data, resulting in a double-free of the underlying decoder context in any FFmpeg-based application using NVDEC hardware-accelerated decoding.