CVE-2021-3566: Debian Linux

Medium severity, CVSS 5.5. EPSS: 0.9% chance of exploitation in the next 30 days.

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).

Affected products

• Debian Debian Linux: version 9.0 only
• Ffmpeg Ffmpeg: before 4.3 (fixed in 4.3)

Published 2021-08-05. Last modified 2026-06-17.