Critical sandbox-escape in widely used Firefox/Thunderbird with CVSS 9.8 enabling arbitrary code execution; impacts many endpoints and requires org-wide mitigation.
CVE-2026-16352
Use-after-free sandbox escape in Firefox/Thunderbird enabling arbitrary code execution.
Is CVE-2026-16352 being exploited?
Not confirmed. CVE-2026-16352 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 0.39% probability of exploitation in the next 30 days.
How severe is CVE-2026-16352?
CVE-2026-16352 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-2026-16352?
Yes. A fix has been recorded for CVE-2026-16352. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-16352 affect?
CVE-2026-16352 affects Firefox 153 (fixed), Firefox ESR 115.38 (fixed), Firefox ESR 140.13 (fixed), Thunderbird 153 (fixed), and 2 further products or versions. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-16352?
Update Firefox/Thunderbird to the listed fixed versions immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Use-after-free in Disability Access APIs allows sandbox escape and arbitrary code execution in browser/email client processes.
Immediate action required