CVE-2026-12300: Mozilla Firefox

Medium severity, CVSS 5.3. EPSS: 0.3% chance of exploitation in the next 30 days.

Memory safety bug fixed in Firefox 152. This vulnerability was fixed in Firefox 152 and Thunderbird 152.

Affected products

• Mozilla Firefox: before 152.0.0 (fixed in 152.0.0)
• Mozilla Thunderbird: before 152.0.0 (fixed in 152.0.0)

Published 2026-06-16. Last modified 2026-06-18.