CVE-2026-0881: Mozilla Firefox

Critical severity, CVSS 10.0. EPSS: 0.4% chance of exploitation in the next 30 days.

Sandbox escape in the Messaging System component. This vulnerability was fixed in Firefox 147 and Thunderbird 147.

Affected products

• Mozilla Firefox: before 147.0 (fixed in 147.0)
• Mozilla Thunderbird: before 147.0 (fixed in 147.0)

Published 2026-01-13. Last modified 2026-07-15.