CVE-2025-9181: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 0.4% chance of exploitation in the next 30 days.

Uninitialized memory in the JavaScript Engine component. This vulnerability was fixed in Firefox 142, Firefox ESR 128.14, Firefox ESR 140.2, Thunderbird 142, Thunderbird 128.14, and Thunderbird 140.2.

Affected products

• Mozilla Firefox: before 128.14.0 (fixed in 128.14.0); before 142.0 (fixed in 142.0); from 140.0, before 140.2.0 (fixed in 140.2.0)
• Mozilla Thunderbird: before 128.14.0 (fixed in 128.14.0); before 142.0 (fixed in 142.0); from 140.0, before 140.2.0 (fixed in 140.2.0)

Published 2025-08-19. Last modified 2026-10-05.