FFmpeg heap reuse after release vulnerability (CNVD-2021-79768)

FFmpeg is a set of open source computer programs that can be used to record, convert, and stream digital audio and video under the LGPL or GPL license. av_freep function in libavutil/mem.c in FFmpeg version 4.2 is vulnerable to a heap-release post-reuse vulnerability. An attacker can exploit this vulnerability to execute arbitrary code.