CVE-2021-3566: 
Ffmpeg vulnerability analysis and mitigation

CVE-2021-3566 is a security vulnerability discovered in FFmpeg's tty demuxer functionality. The vulnerability was disclosed and patched in 2021, affecting FFmpeg multimedia framework installations across various Linux distributions including Ubuntu and Debian (Ubuntu Security, Debian LTS).

The vulnerability stems from the tty demuxer not having a 'read_probe' function assigned to it. This technical oversight allows exploitation through crafted 'ffconcat' files that reference an image followed by a file triggering the tty demuxer, resulting in the contents of the second file being copied verbatim into the output file when using the -vcodec copy option (Debian LTS).

When exploited, this vulnerability could lead to information disclosure as it allows attackers to manipulate file contents through crafted input. The vulnerability specifically affects the handling of data assigned to the tty demuxer, potentially exposing sensitive information (Ubuntu Security).

The vulnerability has been patched in multiple distributions. Ubuntu 16.04 ESM users should update to FFmpeg version 7:2.8.17-0ubuntu0.1+esm4, while Debian 9 (Stretch) users should upgrade to version 7:3.2.15-0+deb9u3. The fix involves implementing a proper read_probe function for the tty demuxer (Ubuntu Security, Debian LTS).