CVE-2026-16389: Mozilla Firefox

Critical severity, CVSS 9.8. EPSS: 0.6% chance of exploitation in the next 30 days.

Incorrect boundary conditions, integer overflow in the Libraries component in NSS. This vulnerability was fixed in Firefox 153 and Thunderbird 153.

Affected products

• Mozilla Firefox: before 153.0.0 (fixed in 153.0.0)
• Mozilla Thunderbird: before 153.0 (fixed in 153.0)

Published 2026-07-21. Last modified 2026-08-10.