CVE-2026-92021: Mozilla Firefox

High severity, CVSS 8.8. EPSS: 0.3% chance of exploitation in the next 30 days.

Use-after-free in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox ESR 140.16 and Thunderbird 140.16.

Affected products

• Mozilla Firefox: before 140.16.0 (fixed in 140.16.0)
• Mozilla Thunderbird: before 140.16.0 (fixed in 140.16.0)

Published 2026-09-15. Last modified 2026-10-06.