CVE-2026-12329: Mozilla Firefox

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

Memory safety bug fixed in Thunderbird ESR 140.12. This vulnerability was fixed in Firefox ESR 140.12 and Thunderbird 140.12.

Affected products

• Mozilla Firefox: from 140.0, before 140.12.0 (fixed in 140.12.0)
• Mozilla Thunderbird: from 140.0, before 140.12.0 (fixed in 140.12.0)

Published 2026-06-16. Last modified 2026-07-15.