Widely-used Firefox/Thunderbird; critical RCE risk; impacts many organizations.
CVE-2026-2799
Use-after-free in Firefox/Thunderbird DOM may allow remote code execution.
Is CVE-2026-2799 being exploited?
Not confirmed. CVE-2026-2799 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 0.32% probability of exploitation in the next 30 days.
How severe is CVE-2026-2799?
CVE-2026-2799 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-2026-2799?
Yes. A fix has been recorded for CVE-2026-2799. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-2799 affect?
CVE-2026-2799 affects Firefox < 148, Thunderbird < 148. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-2799?
Update to the latest Firefox/Thunderbird release.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution via crafted content in Firefox/Thunderbird DOM (pre-148).
Immediate action required