What is CVE-2026-16406?

CVE-2026-16406 is a critical-severity vulnerability in Mozilla Firefox, classified under Protection Mechanism Failure. CVSS score: 9.1/10. Published 2026-07-21.

How severe is CVE-2026-16406?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Vulnerability in Mozilla Firefox

CVE-2026-16406

Mitigation bypass in the Networking component. This vulnerability was fixed in Firefox 153.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

Affected products

Mozilla Firefox — versions 153

Weakness classification (CWE)

CWE-693 — Protection Mechanism Failure

References

security@mozilla.org
security@mozilla.org

Frequently asked questions

What is CVE-2026-16406?: CVE-2026-16406 is a critical-severity vulnerability in Mozilla Firefox, classified under Protection Mechanism Failure. CVSS score: 9.1/10. Published 2026-07-21.
How severe is CVE-2026-16406?: Critical severity. CVSS v3 base score is 9.1 out of 10.