CVE-2021-43540

6.5 mediumEPSS 0.9%

Medium (6.5) in mozilla firefox. EPSS 0.9% chance of exploitation in the next 30 days.

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.

Severity

CVSS 3.1

6.5 medium

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

EPSS: 0.9% chance of exploitation in the next 30 days; higher than 59% of CVEs (scores of 2026-10-31)
Published: 2021-12-08
Modified: 2026-06-17
Record from: the NVD, synced 2026-10-19

Affected

mozilla:firefox

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1636629
https://security.gentoo.org/glsa/202202-03
https://www.mozilla.org/security/advisories/mfsa2021-52/
https://bugzilla.mozilla.org/show_bug.cgi?id=1636629
https://security.gentoo.org/glsa/202202-03

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