Affects widely-used Firefox/Thunderbird; potential remote code execution via web content; high visibility.
CVE-2026-2764
Critical RCE via JIT use-after-free in Firefox/Thunderbird JS engine
Is CVE-2026-2764 being exploited?
Not confirmed. CVE-2026-2764 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 0.47% probability of exploitation in the next 30 days.
How severe is CVE-2026-2764?
CVE-2026-2764 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-2026-2764?
Yes. A fix has been recorded for CVE-2026-2764. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-2764 affect?
CVE-2026-2764 affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, 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-2026-2764?
Update to patched versions when released
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution via crafted content; attacker could run code with user privileges.
Patch when possible