What’s Vulnerable › Vulnerabilities

CVE-2021-43540

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-12-08 · updated 2026-06-17

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.

Affected products

• Mozilla Firefox: before 95.0 — fixed in 95.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 95.0. Check the vendor advisory for mitigations.

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
• https://www.mozilla.org/security/advisories/mfsa2021-52/

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