CVE-2026-16388: Mozilla Firefox

Critical severity, CVSS 9.8. EPSS: 0.4% chance of exploitation in the next 30 days.

Sandbox escape in the DOM: Networking component. 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 2026-07-24.