CVE-2026-12302: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 0.2% chance of exploitation in the next 30 days.

Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.

Affected products

• Mozilla Firefox: before 140.12.0 (fixed in 140.12.0); before 152.0.0 (fixed in 152.0.0)
• Mozilla Thunderbird: before 140.12.0 (fixed in 140.12.0); before 152.0.0 (fixed in 152.0.0)

Published 2026-06-16. Last modified 2026-06-17.