JLSEC-2025-103 Medium 6.5

A denial of service in the subtitle decoder in FFmpeg 3.2 and 4.1 allows attackers to hog the CPU...

JLSEC Published: Oct 19, 2025
Modified: Jul 23, 2026
Severity: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Affected Packages: FFMPEG_jll < 4.3.1+0
Upstream: CVE-2019-9721

A denial of service in the subtitle decoder in FFmpeg 3.2 and 4.1 allows attackers to hog the CPU via a crafted video file in Matroska format, because handle_open_brace in libavcodec/htmlsubtitles.c has a complex format argument to sscanf.

References

http://www.securityfocus.com/bid/107384
https://git.ffmpeg.org/gitweb/ffmpeg.git/commit/894995c41e0795c7a44f81adc4838dedc3932e65
https://github.com/FFmpeg/FFmpeg/commit/273f2755ce8635d42da3cde0eeba15b2e7842774
https://usn.ubuntu.com/3967-1/