CVE-2021-29976

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

Description

Mozilla developers reported memory safety bugs present in code shared between Firefox and Thunderbird. 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 Thunderbird < 78.12, Firefox ESR < 78.12, and Firefox < 90.

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-2021:2743

vendor Authored 2026-05-27

Vendor advisory: rocky — https://errata.rockylinux.org/RLSA-2021:2883

vendor Authored 2026-05-27

Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2021-29976

vendor Authored 2026-05-27

Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2021-29976.html

vendor Authored 2026-05-27

Vendor advisory: arch — https://security.archlinux.org/ASA-202107-20

vendor Authored 2026-05-27

Vendor advisory: arch — https://security.archlinux.org/ASA-202107-21

OS impact

OSVersionStatusFixed in
arch archfixed78.12.0-1
suse slesaffected
debian debiansidfixed90.0-1
debian debianbookwormfixed78.12.0esr-1
debian debianbullseyefixed78.12.0esr-1
debian debianforkyfixed78.12.0esr-1
debian debiantrixiefixed78.12.0esr-1
rockylinux rocky8fixed

References

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