RCE in widely used Mozilla products (Firefox/Thunderbird). Client-side exploit can impact many users and enterprise endpoints; requires broad IT notification.
CVE-2026-16402
Integer overflow in ImageLib enables RCE via crafted images
Is CVE-2026-16402 being exploited?
Not confirmed. CVE-2026-16402 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 0.34% probability of exploitation in the next 30 days.
How severe is CVE-2026-16402?
CVE-2026-16402 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-2026-16402?
Yes. A fix has been recorded for CVE-2026-16402. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-16402 affect?
CVE-2026-16402 affects Mozilla Firefox <153, Mozilla Thunderbird <153. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-16402?
Update Firefox and Thunderbird to version 153 immediately
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution via crafted image parsing in browser/email client, allowing arbitrary code execution or crash and potential sandbox escape.
Immediate action required