CVE-2021-3566Prior to ffmpeg version 4.3, the tty demuxer did not have a 'read_probe' function assigned to it. By crafting a legitimate "ffconcat" file…
- 5.5MediumCVSS base score
- 0.88%Exploitation in 30 daysEPSS · top 40% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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).
Timeline
ID reserved
By fedora
- 2 months later
· 2 months later
Published
- 3 years later
· 3 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | Medium5.5 | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N |
- EPSS (exploitation in 30 days)
- 0.88% · top 40% of all CVEs (15 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.
Affected products
ffmpeg
- affected ffmpeg 4.3
References
References2
- https://github.com/FFmpeg/FFmpeg/commit/3bce9e9b3ea35c54bacccc793d7da99ea5157532#diff-74f6b92a0541378ad15de9c29c0a2b0c69881ad9ffc71abe568b88b535e00a7f (opens in a new tab)x_refsource_MISCx_transferred
- [debian-lts-announce] 20210815 [SECURITY] [DLA 2742-1] ffmpeg security update (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2021-26876 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2021-3566)Record last updated .