A use-after-free vulnerability was found via testing, and traced to an out-of-date Cairo library.

published 2021-08-05 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-16431

cvss: 8.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.0%; EPSS 1.0% chance of exploitation in 30 days, percentile 64%
public exploits: 0; none known

A use-after-free vulnerability was found via testing, and traced to an out-of-date Cairo library. Updating the library resolved the issue, and may have remediated other, unknown security vulnerabilities as well. This vulnerability affects Firefox < 90.

Patch / fix

fixed in 1 distros 4

Mozilla Firefox 90

ubuntu opensuse alpine arch linux

firefox Ubuntu 18.04 LTS 90.0+build1-0ubuntu0.18.04.1
firefox Ubuntu 20.04 LTS 90.0+build1-0ubuntu0.20.04.1

ubuntu advisories UBUNTU-CVE-2021-29972

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

firefox-esr openSUSE Tumbleweed 128.5.1-1.1
MozillaFirefox openSUSE Tumbleweed 92.0-1.2

opensuse advisories openSUSE-SU-2024:14572-1 openSUSE-SU-2024:10600-1

firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +6 more 90.0-r0
librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 90.0-r0

alpine advisories ALPINE-CVE-2021-29972

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

firefox Arch Linux 90.0-1

arch linux advisories AVG-2148

Exploit prediction

1.04% chance of exploitation in the next 30 days, higher than 64% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

bugzilla.mozilla.org https://bugzilla.mozilla.org/show_bug.cgi?id=1696816 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	8.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD	2.0	6.8	AV:N/AC:M/Au:N/C:P/I:P/A:P

Affected products

Mozilla Firefox

Classification

Weakness

CWE-416 Use After Free

References

bugzilla.mozilla.org /show_bug.cgi?id=1696816
exploit, issue-tracking, vendor-advisory
security.gentoo.org /glsa/202202-03
vendor-advisory, third-party-advisory
mozilla.org /security/advisories/mfsa2021-28/
vendor-advisory

Sources

CVE List CVE-2021-29972
NVD CVE-2021-29972

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