Prior to ffmpeg version 4.3, the tty demuxer did not have a 'read_probe' function assigned to it. By crafting a legitimate "ffconcat" file that references an image, followed by a file the triggers the tty demuxer, the contents of the second file will be copied into the output file verbatim (as long as the `-vcodec copy` option is passed to ffmpeg). CREATE(Triage):(User=admin) CVE-2021-3566 (https://nvd.nist.gov/vuln/detail/CVE-2021-3566)
