CVE-2021-43540

high

Published — · Modified —

CVSS v3

—

CVSS v2

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VIR risk

8.0

Description

WebExtensions with the correct permissions were able to create and install ServiceWorkers for third-party websites that would not have been uninstalled with the extension. This vulnerability affects Firefox < 95.

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-2021-43540

vendor Authored 2026-05-27

Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2021-43540.html

vendor Authored 2026-05-27

Vendor advisory: arch — https://security.archlinux.org/ASA-202112-8

OS impact

OS	Version	Status	Fixed in
arch		fixed	`95.0-1`
sles		affected
debian	sid	fixed	`95.0-1`

References

https://security.archlinux.org/ASA-202112-8
https://www.suse.com/security/cve/CVE-2021-43540.html
https://security-tracker.debian.org/tracker/CVE-2021-43540

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