CVE-2026-16357
Critical RCE in Firefox/Thunderbird via crafted graphics (CWE-119).
Is CVE-2026-16357 being exploited?
Not confirmed. CVE-2026-16357 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 0.40% probability of exploitation in the next 30 days.
How severe is CVE-2026-16357?
CVE-2026-16357 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-2026-16357?
Yes. A fix has been recorded for CVE-2026-16357. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-16357 affect?
CVE-2026-16357 affects Mozilla Firefox < 153, Firefox ESR < 115.38, Firefox ESR < 140.13, Mozilla 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-2026-16357?
Update to Firefox 153+/ESR 115.38+/140.13+ and Thunderbird 153+/140.13+ immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution in browser or mail client via crafted graphics content, allowing arbitrary code execution in the affected process.
Immediate action required