CVE-2026-2791: Mozilla Firefox

Critical severity, CVSS 9.8. EPSS: 0.5% chance of exploitation in the next 30 days.

Mitigation bypass in the Networking: Cache component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

Affected products

• Mozilla Firefox: before 140.8.0 (fixed in 140.8.0); before 148.0 (fixed in 148.0)
• Mozilla Thunderbird: before 140.8.0 (fixed in 140.8.0); before 148.0 (fixed in 148.0)

Published 2026-02-24. Last modified 2026-06-17.