CVE-2026-4723: Mozilla Firefox

Critical severity, CVSS 9.8. EPSS: 0.5% chance of exploitation in the next 30 days.

Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 149 and Thunderbird 149.

Affected products

• Mozilla Firefox: before 149.0 (fixed in 149.0)

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