An integer overflow vulnerability was found in FFmpeg versions before 4.4.2 and before 5.0.1 in g729_parse() in llibavcodec/g729_parser.c when processing a specially crafted file.
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).