Critical mitigation bypass in Firefox (widely used browser) with CVSS 9.1 could enable high-impact exploitation across enterprises.
CVE-2026-16406
Firefox networking mitigation bypass allowing high-impact exploitation.
Is CVE-2026-16406 being exploited?
Not confirmed. CVE-2026-16406 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.25% probability of exploitation in the next 30 days.
How severe is CVE-2026-16406?
CVE-2026-16406 is rated Critical with a CVSS score of 9.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-16406?
Yes. A fix has been recorded for CVE-2026-16406. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-16406 affect?
CVE-2026-16406 affects Mozilla Firefox < 153. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-16406?
Update Firefox to version 153 or later immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Bypass of Firefox networking mitigations enabling remote code execution, sandbox escape, or exposure of network data via crafted network content.
Immediate action required