CVE-2026-6771
DOM mitigation bypass in Firefox/Thunderbird security component.
Is CVE-2026-6771 being exploited?
Not confirmed. CVE-2026-6771 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 0.31% probability of exploitation in the next 30 days.
How severe is CVE-2026-6771?
CVE-2026-6771 is rated Critical with a CVSS score of 9.8. 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-2026-6771?
Yes. A fix has been recorded for CVE-2026-6771. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-6771 affect?
CVE-2026-6771 affects Mozilla Firefox 150.x, Firefox ESR 140.10, Mozilla Thunderbird 150.x, Thunderbird 140.10. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-6771?
Update to patched versions (Firefox 150+/Thunderbird 150+).
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Bypasses DOM security mitigations; could enable attacker-controlled actions via crafted web content.
Immediate action required