CVE-2020-12387

critical
Published — · Modified —
CVSS v3
CVSS v2
VIR risk
9.5

Description

A race condition when running shutdown code for Web Worker led to a use-after-free vulnerability. This resulted in a potentially exploitable crash. This vulnerability affects Firefox ESR < 68.8, Firefox < 76, and Thunderbird < 68.8.0.

Predictions

Exploit likelihood
20%
Patch ETA

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

vendor Authored 2026-05-27

Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2020-12387

vendor Authored 2026-05-27

Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2020-12387.html

vendor Authored 2026-05-27

Vendor advisory: arch — https://security.archlinux.org/ASA-202005-3

vendor Authored 2026-05-27

Vendor advisory: arch — https://security.archlinux.org/ASA-202005-7

OS impact

OSVersionStatusFixed in
arch archfixed68.8.0-1
suse slesaffected
debian debiansidfixed76.0-1
debian debianbookwormfixed68.8.0esr-1
debian debianbullseyefixed68.8.0esr-1
debian debianforkyfixed68.8.0esr-1
debian debiantrixiefixed68.8.0esr-1

References

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