What is CVE-2026-100819?

CVE-2026-100819 is a critical-severity vulnerability, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.6/10. Published 2026-09-29.

How severe is CVE-2026-100819?

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

CVE-2026-100819

CVE-2026-100819

Sandbox escape due to incorrect boundary conditions in the XPCOM component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

Vulnerability class: Buffer Overflow

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-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer

References

Frequently asked questions

What is CVE-2026-100819?: CVE-2026-100819 is a critical-severity vulnerability, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.6/10. Published 2026-09-29.
How severe is CVE-2026-100819?: Critical severity. CVSS v3 base score is 9.6 out of 10.