CVE-2025-2857: Mozilla Firefox

Critical severity, CVSS 10.0. EPSS: 1.9% chance of exploitation in the next 30 days.

Following the recent Chrome sandbox escape (CVE-2025-2783), various Firefox developers identified a similar pattern in our IPC code. A compromised child process could cause the parent process to return an unintentionally powerful handle, leading to a sandbox escape. The original vulnerability was being exploited in the wild. *This only affects Firefox on Windows. Other operating systems are unaffected.*. This vulnerability was fixed in Firefox 136.0.4, Firefox ESR 128.8.1, and Firefox ESR 115.21.1.

Affected products

• Mozilla Firefox: before 136.0.4 (fixed in 136.0.4); before 115.21.1 (fixed in 115.21.1); from 128.1.0, before 128.8.1 (fixed in 128.8.1)

Published 2025-03-27. Last modified 2026-10-05.