What is CVE-2026-100811?

CVE-2026-100811 is a critical-severity vulnerability, classified under Use After Free. CVSS score: 9.6/10. Published 2026-09-29.

How severe is CVE-2026-100811?

Critical severity. CVSS v3 base score is 9.6 out of 10.

CVE-2026-100811

CVE-2026-100811

Sandbox escape due to use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17.

Vulnerability class: Use-After-Free

Published 2026-09-29 · last modified 2026-09-30.

CVSS v3 metric

CVSS v3 base score 9.6 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Weakness classification (CWE)

CWE-416 — Use After Free

References

bugzilla.mozilla.org/show_bug.cgi
www.mozilla.org/security/advisories/mfsa2026-100/
www.mozilla.org/security/advisories/mfsa2026-97/
www.mozilla.org/security/advisories/mfsa2026-99/

Frequently asked questions

What is CVE-2026-100811?: CVE-2026-100811 is a critical-severity vulnerability, classified under Use After Free. CVSS score: 9.6/10. Published 2026-09-29.
How severe is CVE-2026-100811?: Critical severity. CVSS v3 base score is 9.6 out of 10.