CVE-2021-43535

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

Description

A use-after-free could have occured when an HTTP2 session object was released on a different thread, leading to memory corruption and a potentially exploitable crash. This vulnerability affects Firefox < 93, 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-2021-43535

OS impact

OSVersionStatusFixed in
debian debiansidfixed93.0-1
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.