CVE-2026-75874: Mozilla Firefox

Critical severity, CVSS 10.0. EPSS: 0.5% chance of exploitation in the next 30 days.

Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154, Thunderbird 154, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 140.15, and Thunderbird 153.2.

Affected products

• Mozilla Firefox: before 154.0.0 (fixed in 154.0.0)
• Mozilla Thunderbird: before 154.0 (fixed in 154.0)

Published 2026-08-18. Last modified 2026-09-01.