CVE-2026-12330: Mozilla Firefox

Medium severity, CVSS 5.4. EPSS: 0.2% chance of exploitation in the next 30 days.

Incorrect boundary conditions in the Internationalization component. This vulnerability was fixed in Firefox ESR 140.12, Firefox ESR 115.37, and Thunderbird 140.12.

Affected products

• Mozilla Firefox: before 115.37.0 (fixed in 115.37.0); from 140.0, before 140.12.0 (fixed in 140.12.0)
• Mozilla Thunderbird: from 140.0, before 140.12.0 (fixed in 140.12.0)

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