Vulnerability in Mozilla Firefox
CVE-2026-16399
Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 153 and Thunderbird 153.
EPSS: 0.001 (4.4th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
Affected products
- Mozilla Firefox — versions 153
- Mozilla Thunderbird — versions 153
Weakness classification (CWE)
References
- security@mozilla.org (Permissions Required)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org (Vendor Advisory)
Frequently asked questions
- What is CVE-2026-16399?
- CVE-2026-16399 is a high-severity vulnerability in Mozilla Firefox, classified under Origin Validation Error. CVSS score: 7.5/10. Published 2026-07-21.
- How severe is CVE-2026-16399?
- High severity. CVSS v3 base score is 7.5 out of 10.