Vulnerability in Mozilla Firefox
CVE-2026-12299
JIT miscompilation in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N.
Affected products
- Mozilla Firefox — versions 115.37, 140.12, 152
- Mozilla Thunderbird — versions 140.12, 152
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-12299?
- CVE-2026-12299 is a medium-severity vulnerability in Mozilla Firefox, classified under Access of Resource Using Incompatible Type (Type Confusion). CVSS score: 5.4/10. Published 2026-06-16.
- How severe is CVE-2026-12299?
- Medium severity. CVSS v3 base score is 5.4 out of 10.