CVE-2026-8946: Mozilla Firefox

High severity, CVSS 7.5. EPSS: 0.6% chance of exploitation in the next 30 days.

Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 151, Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

Affected products

• Mozilla Firefox: before 115.36.0 (fixed in 115.36.0); before 151.0.0 (fixed in 151.0.0); from 140.0, before 140.11.0 (fixed in 140.11.0)
• Mozilla Thunderbird: before 140.11 (fixed in 140.11)

Published 2026-05-19. Last modified 2026-07-15.