CVE-2026-16353
Use-after-free in Firefox/Thunderbird WebIDL DOM bindings enabling remote code execution.
Is CVE-2026-16353 being exploited?
Not confirmed. CVE-2026-16353 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 0.52% probability of exploitation in the next 30 days.
How severe is CVE-2026-16353?
CVE-2026-16353 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-2026-16353?
Yes. A fix has been recorded for CVE-2026-16353. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-16353 affect?
CVE-2026-16353 affects Firefox < 153, Firefox ESR < 115.38, Firefox ESR < 140.13, Thunderbird < 153, and 1 further product or version. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-16353?
Immediately update Firefox/Thunderbird to the fixed versions and enforce browser update policy.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution via crafted web content exploiting invalid pointer in WebIDL (use-after-free/null deref), allowing code execution or sandbox escape.
Immediate action required