CVE-2025-3034: Mozilla Firefox

High severity, CVSS 8.1. EPSS: 0.5% chance of exploitation in the next 30 days.

Memory safety bugs present in Firefox 136 and Thunderbird 136. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 137 and Thunderbird 137.

Affected products

• Mozilla Firefox: before 137.0 (fixed in 137.0)
• Mozilla Thunderbird: before 137.0 (fixed in 137.0)

Published 2025-04-01. Last modified 2026-09-30.