CVE-2026-84131
Privilege escalation in Firefox/Thunderbird graphics component.
Is CVE-2026-84131 being exploited?
Not confirmed. CVE-2026-84131 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 0.33% probability of exploitation in the next 30 days.
How severe is CVE-2026-84131?
CVE-2026-84131 is rated High with a CVSS score of 8.8. 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-2026-84131?
Yes. A fix has been recorded for CVE-2026-84131. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-84131 affect?
CVE-2026-84131 affects Firefox 155 (fixed), Firefox ESR 115.40 (fixed), Firefox ESR 140.15 (fixed), Firefox ESR 153.2 (fixed), and 3 further products or versions. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-84131?
Update Firefox/Thunderbird to the fixed versions immediately; restrict untrusted graphics content until patched.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Invalid pointer in graphics can allow local privilege escalation and potential sandbox escape to execute code with higher privileges.
Patch when possible