Is CVE-2021-43540 in the CISA KEV catalog?

No. CVE-2021-43540 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-43540?

CVE-2021-43540 has a CVSS v3 base score of 6.5 (MEDIUM).

What is the EPSS score for CVE-2021-43540?

CVE-2021-43540 has an EPSS score of 0.86% (54th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-43540?

Upgrade firefox on debian unstable to 95.0-1 or later. Fixes are available for 4 affected products.

CVE & CISA-KEV Catalog

CVE-2021-43540

MEDIUM

6.5

CVSS v3

NVD

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.

How to fix

Remediation Available

firefoxDebian

Fixed in:95.0-1CVE-2021-43540

firefoxUbuntu

Fixed in:95.0+build1-0ubuntu0.18.04.1USN-5186-1

Fixed in:95.0+build1-0ubuntu0.20.04.1USN-5186-1

DeveloperEditionWindows application

Affected:95.0Fixed in:95.0Mozilla

Mozilla Firefox (en-US)Windows application

Affected:95.0Fixed in:95.0Mozilla

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityHigh

AvailabilityNone

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

Exploit Intelligence

0.86%probability of exploitation in 30 days

54thpercentile

Moderate risk: more likely to be exploited than 54% of all known CVEs.

References

Vendor Advisory2

Third-Party Advisory1

security.gentoo.org

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.