CVE-2021-43534

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

Description

Mozilla developers and community members reported memory safety bugs present in Firefox 93 and Firefox ESR 91.2. 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 < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.

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-2021:4123

vendor Authored 2026-05-27

Vendor advisory: rocky — https://errata.rockylinux.org/RLSA-2021:4130

vendor Authored 2026-05-27

Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2021-43534

OS impact

OSVersionStatusFixed in
debian debiansidfixed94.0-1
debian debianbookwormfixed91.3.0esr-1
debian debianbullseyefixed91.4.1esr-1~deb11u1
debian debianforkyfixed91.3.0esr-1
debian debiantrixiefixed91.3.0esr-1
rockylinux rocky8fixed

References

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