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Fencer Vulns
medium 6.5

CVE-2019-9721 json

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

published 2019-03-12 7 y ago modified 2026-07-23 3 mo ago also EUVD-2019-19086 , JLSEC-2025-103

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.4%
EPSS 1.4% chance of exploitation in 30 days, percentile 73%
public exploits
0
none known

Summary

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.

Patch / fix

  • julia FFMPEG_jll 4.3.1+0
  • ffmpeg Debian 14, Debian 13, Debian 12 7:4.1.3-1

debian advisories DEBIAN-CVE-2019-9721

  • ffmpeg Ubuntu 18.04 LTS 7:3.4.6-0ubuntu0.18.04.1

ubuntu advisories UBUNTU-CVE-2019-9721

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • ffmpeg SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +10 more 3.4.2-4.34.2
  • ffmpeg SLE Workstation Extension 15 SP3, SLE Workstation Extension 15 SP2, SLE Module for Package Hub 15 SP3 +3 more 3.4.2-11.8.2

suse advisories SUSE-SU-2021:2929-1SUSE-SU-2021:2919-1

  • ffmpeg openSUSE Leap 15.3 3.4.2-11.8.2

opensuse advisories openSUSE-SU-2021:2919-1

  • ffmpeg Alpine 3.24, Alpine 3.23, Alpine 3.22 +12 more 4.1.3-r0
  • ffmpeg Alpine 3.8 3.4.6-r0
  • ffmpeg Alpine 3.9 4.0.4-r0
  • ffmpeg4 Alpine 3.22, Alpine 3.21, Alpine 3.20 +4 more 4.1.3-r0

alpine advisories ALPINE-CVE-2019-9721

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2019-9721 updated cvss 4.3

ffmpeg: complex format argument in handle_open_brace in libavcodec/htmlsubtitles.c causing denial of service

  • Red Hat Enterprise Linux 5 qffmpeg
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.44% chance of exploitation in the next 30 days, higher than 73% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:N/A:P
OSV 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
julia FFMPEG_jll
<4.3.1+0
4.3.1+0

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.