Affects widely-used Firefox browser; sandbox escape could lead to remote code execution in many environments.
CVE-2026-0879
Sandbox escape in Firefox graphics component.
Is CVE-2026-0879 being exploited?
Not confirmed. CVE-2026-0879 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 0.61% probability of exploitation in the next 30 days.
How severe is CVE-2026-0879?
CVE-2026-0879 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-2026-0879?
Yes. A fix has been recorded for CVE-2026-0879. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-0879 affect?
CVE-2026-0879 affects Firefox < 147, Firefox ESR < 115.32, Firefox ESR < 140.7. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-0879?
Patch to Firefox 147+ or ESR 115.32+/140.7+ immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Sandbox escape enables arbitrary code execution in the browser via the graphics component.
Immediate action required