CVE-2026-16379
Privilege escalation in Firefox/Thunderbird content processes.
Is CVE-2026-16379 being exploited?
Not confirmed. CVE-2026-16379 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 0.28% probability of exploitation in the next 30 days.
How severe is CVE-2026-16379?
CVE-2026-16379 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-2026-16379?
Yes. A fix has been recorded for CVE-2026-16379. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-16379 affect?
CVE-2026-16379 affects Mozilla Firefox < 153, Firefox ESR < 140.13, Mozilla Thunderbird < 153, Thunderbird ESR < 140.13. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-16379?
Update to Firefox 153 / ESR 140.13 and Thunderbird 153 / ESR 140.13 immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Allows web content or a local attacker to escalate privileges in content processes, potentially escaping sandbox and performing elevated actions.
Immediate action required