CVE-2026-100822: Mozilla Firefox

Medium severity, CVSS 5.4. EPSS: 0.2% chance of exploitation in the next 30 days.

Spoofing issue in the Networking: HTTP component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.

Affected products

• Mozilla Firefox
• Mozilla Thunderbird

Published 2026-09-29. Last modified 2026-09-30.