CVE-2026-84132: Mozilla Firefox

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

Information disclosure in the Networking: HTTP component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.

Affected products

• Mozilla Firefox: before 153.2.0 (fixed in 153.2.0); from 154.0.0, before 155.0.0 (fixed in 155.0.0)
• Mozilla Thunderbird: before 153.2.0 (fixed in 153.2.0); from 154.0, before 155.0 (fixed in 155.0)

Published 2026-09-01. Last modified 2026-09-03.