CVE-2025-1931: Mozilla Firefox

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

It was possible to cause a use-after-free in the content process side of a WebTransport connection, leading to a potentially exploitable crash. This vulnerability was fixed in Firefox 136, Firefox ESR 115.21, Firefox ESR 128.8, Thunderbird 136, and Thunderbird 128.8.

Affected products

• Mozilla Firefox: before 115.21.0 (fixed in 115.21.0); before 136.0 (fixed in 136.0); from 116.0, before 128.8.0 (fixed in 128.8.0)
• Mozilla Thunderbird: before 128.8.0 (fixed in 128.8.0); from 129.0, before 136.0 (fixed in 136.0)

Published 2025-03-04. Last modified 2026-10-05.