What is CVE-2026-92071?

CVE-2026-92071 is a critical-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.6/10. Published 2026-09-15.

How severe is CVE-2026-92071?

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

Buffer overflow in Mozilla Firefox

CVE-2026-92071

Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component. This vulnerability was fixed in Firefox 156, Firefox ESR 153.3, Thunderbird 156, and Thunderbird 153.3.

Vulnerability class: Buffer Overflow

Published 2026-09-15 · last modified 2026-10-05.

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

EPSS: 0.002 (15.0th percentile), scored 2026-10-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 15th percentile — 15.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.002 · change: -0.000

Affected products

Weakness classification (CWE)

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

References

bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
www.mozilla.org/security/advisories/mfsa2026-90/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2026-93/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2026-94/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2026-96/ (Vendor Advisory)

Frequently asked questions

What is CVE-2026-92071?: CVE-2026-92071 is a critical-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.6/10. Published 2026-09-15.
How severe is CVE-2026-92071?: Critical severity. CVSS v3 base score is 9.6 out of 10.