CVE-2026-8962
Mitigation bypass in Firefox/Thunderbird DOM security component.
Is CVE-2026-8962 being exploited?
Not confirmed. CVE-2026-8962 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 0.37% probability of exploitation in the next 30 days.
How severe is CVE-2026-8962?
CVE-2026-8962 is rated High with a CVSS score of 8.1. 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-2026-8962?
Yes. A fix has been recorded for CVE-2026-8962. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-8962 affect?
CVE-2026-8962 affects Firefox 151, Firefox ESR 140.11, Thunderbird 151, Thunderbird 140.11. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-8962?
Update to patched Firefox/Thunderbird versions.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Bypass DOM security mitigations via crafted web content; could lower protections and enable browser exploits.
Patch when possible