Widely used browser sandbox escape; could lead to host compromise; affects Firefox/Thunderbird.
CVE-2026-12294
Firefox/Thunderbird DOM Workers sandbox escape.
Is CVE-2026-12294 being exploited?
Not confirmed. CVE-2026-12294 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 0.36% probability of exploitation in the next 30 days.
How severe is CVE-2026-12294?
CVE-2026-12294 is rated Critical with a CVSS score of 9.6. 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-2026-12294?
Yes. A fix has been recorded for CVE-2026-12294. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-12294 affect?
CVE-2026-12294 affects Firefox, Thunderbird. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-12294?
Update to patched Firefox/Thunderbird releases ASAP
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Sandbox escape allows arbitrary code execution via malicious content, breaking the browser sandbox.
Patch when possible