CVE-2021-4129

high
Published — · Modified —
CVSS v3
CVSS v2
VIR risk
8.0

Description

Mozilla developers and community members Julian Hector, Randell Jesup, Gabriele Svelto, Tyson Smith, Christian Holler, and Masayuki Nakano reported memory safety bugs present in Firefox 94. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 95, Firefox ESR < 91.4.0, and Thunderbird < 91.4.0.

Predictions

Exploit likelihood
20%
Patch ETA

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

vendor Authored 2026-05-27

Vendor advisory: rocky — https://errata.rockylinux.org/RLSA-2021:5013

vendor Authored 2026-05-27

Vendor advisory: rocky — https://errata.rockylinux.org/RLSA-2021:5045

vendor Authored 2026-05-27

Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2021-4129

OS impact

OSVersionStatusFixed in
debian debiansidfixed95.0-1
debian debianbookwormfixed91.4.0esr-1
debian debianbullseyefixed91.4.1esr-1~deb11u1
debian debianforkyfixed91.4.0esr-1
debian debiantrixiefixed91.4.0esr-1
rockylinux rocky8fixed

References

Verify integrity in audit chain (admin only). AS-IS.