CVE-2025-9184: Mozilla Firefox

High severity, CVSS 8.1. EPSS: 0.4% chance of exploitation in the next 30 days.

Memory safety bugs present in Firefox ESR 140.1, Thunderbird ESR 140.1, Firefox 141 and Thunderbird 141. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 142, Firefox ESR 140.2, Thunderbird 142, and Thunderbird 140.2.

Affected products

• Mozilla Firefox: before 140.2.0 (fixed in 140.2.0); before 142.0 (fixed in 142.0)
• Mozilla Thunderbird: before 140.2.0 (fixed in 140.2.0); before 142.0 (fixed in 142.0)

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