CVE-2025-0237: Mozilla Firefox

Medium severity, CVSS 5.4. EPSS: 0.6% chance of exploitation in the next 30 days.

The WebChannel API, which is used to transport various information across processes, did not check the sending principal but rather accepted the principal being sent. This could have led to privilege escalation attacks. This vulnerability was fixed in Firefox 134, Firefox ESR 128.6, Thunderbird 134, and Thunderbird 128.6.

Affected products

• Mozilla Firefox: before 128.6.0 (fixed in 128.6.0); before 134.0 (fixed in 134.0)
• Mozilla Thunderbird: before 128.6.0 (fixed in 128.6.0); from 129.0, before 134.0 (fixed in 134.0)

Published 2025-01-07. Last modified 2026-10-05.