CVE-2026-12326: Mozilla Firefox

High severity, CVSS 8.1. EPSS: 0.4% chance of exploitation in the next 30 days.

Memory safety bugs present in Firefox 151 and Thunderbird 151. 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 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 2026-07-15.