CVE-2026-12290
Memory safety bug in Thunderbird/Firefox fixed in latest releases.
Is CVE-2026-12290 being exploited?
Not confirmed. CVE-2026-12290 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-2026-12290?
CVE-2026-12290 is rated High with a CVSS score of 8.1. 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-2026-12290?
Yes. A fix has been recorded for CVE-2026-12290. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-12290 affect?
CVE-2026-12290 affects Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, 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-2026-12290?
Update to fixed versions (Firefox 152, ESR 140.12; Thunderbird 152).
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Memory corruption could crash or enable remote code execution; patched in Firefox 152 and Thunderbird 152 (ESR 140.12).
Patch when possible