A heap-use-after-free in the mpeg_mux_write_packet function in libavformat/mpegenc.c of FFmpeg 4.2 allows to cause a denial of service (DOS…

published 2021-08-10 5 y ago modified 2026-06-17 4 mo ago also EUVD-2020-14465

cvss: 6.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.9%; EPSS 0.9% chance of exploitation in 30 days, percentile 60%
public exploits: 0; none known

A heap-use-after-free in the mpeg_mux_write_packet function in libavformat/mpegenc.c of FFmpeg 4.2 allows to cause a denial of service (DOS) via a crafted avi file.

Patch / fix

distros 4 links 1

debian ubuntu suse opensuse

ffmpeg Debian 14, Debian 13, Debian 12 7:4.4-5

debian advisories DEBIAN-CVE-2020-21697

ffmpeg Ubuntu 18.04 LTS 7:3.4.11-0ubuntu0.1
ffmpeg Ubuntu 20.04 LTS 7:4.2.7-0ubuntu0.1
ffmpeg Ubuntu Pro 16.04 LTS 7:2.8.17-0ubuntu0.1+esm2

ubuntu advisories UBUNTU-CVE-2020-21697

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

ffmpeg openSUSE Leap 15.3 3.4.2-11.8.2

opensuse advisories openSUSE-SU-2021:2919-1

trac.ffmpeg.org/ticket/8188 advisory

Exploit prediction

0.92% chance of exploitation in the next 30 days, higher than 60% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

trac.ffmpeg.org https://trac.ffmpeg.org/ticket/8188 referenced PoC, tagged "exploit" by a source, unverified

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

Classification

Weakness

CWE-416 Use After Free

References

trac.ffmpeg.org /ticket/8188
exploit, issue-tracking, patch, vendor-advisory
debian.org /security/2021/dsa-4998
vendor-advisory, third-party-advisory

Sources

CVE List CVE-2020-21697
NVD CVE-2020-21697

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.

Summary