CVE-2026-4727: Mozilla Firefox

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

Denial-of-service in the Libraries component in NSS. This vulnerability was fixed in Firefox 149 and Thunderbird 149.

Affected products

• Mozilla Firefox: before 149.0 (fixed in 149.0)
• Mozilla Thunderbird: before 149.0 (fixed in 149.0)

Published 2026-03-24. Last modified 2026-06-17.