CVE-2026-12327
Memory safety bugs in Firefox/Thunderbird could allow remote code execution.
Is CVE-2026-12327 being exploited?
Not confirmed. CVE-2026-12327 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 0.41% probability of exploitation in the next 30 days.
How severe is CVE-2026-12327?
CVE-2026-12327 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-2026-12327?
Yes. A fix has been recorded for CVE-2026-12327. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-12327 affect?
CVE-2026-12327 affects Firefox ESR 140.11, Thunderbird ESR 140.11, Firefox 151, Thunderbird 151. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-12327?
Update to patched versions (Firefox 152/ESR 140.12, Thunderbird 152/140.12).
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution via memory corruption in Firefox/Thunderbird; attacker could run arbitrary code.
Patch when possible