CVE-2021-3566 Information disclosure in ffmpeg

What is CVE-2021-3566?

CVE-2021-3566 is a medium-severity vulnerability in Debian Debian Linux, published on 5 Aug 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

Official description

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).

Weakness: CWE-200

Which versions are affected by CVE-2021-3566?

It affects 2 products.

Products include Debian Debian Linux, Ffmpeg Ffmpeg.

How do I fix CVE-2021-3566?

Upgrade to a fixed version.

Is CVE-2021-3566 being exploited?

There is no known exploitation of CVE-2021-3566 in the wild and no public exploit code.

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All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2021-3566, GHSA-742p-65hp-7vgf, JLSEC-2025-116, UBUNTU-CVE-2021-3566.