CVE-2025-9179: Mozilla Firefox

Critical severity, CVSS 9.8. EPSS: 0.6% chance of exploitation in the next 30 days.

An attacker was able to perform memory corruption in the GMP process which processes encrypted media. This process is also heavily sandboxed, but represents slightly different privileges from the content process. This vulnerability was fixed in Firefox 142, Firefox ESR 115.27, Firefox ESR 128.14, Firefox ESR 140.2, Thunderbird 142, Thunderbird 128.14, and Thunderbird 140.2.

Affected products

• Mozilla Firefox: before 115.27.0 (fixed in 115.27.0); before 142.0 (fixed in 142.0); from 128.0, before 128.14.0 (fixed in 128.14.0); 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.