What is CVE-2026-92039?

CVE-2026-92039 is a medium-severity vulnerability in Mozilla Firefox, classified under Protection Mechanism Failure. CVSS score: 6.3/10. Published 2026-09-15.

How severe is CVE-2026-92039?

Medium severity. CVSS v3 base score is 6.3 out of 10.

Vulnerability in Mozilla Firefox

CVE-2026-92039

Mitigation bypass in the DOM: Notifications component. This vulnerability was fixed in Firefox 156, Firefox ESR 153.3, Thunderbird 156, and Thunderbird 153.3.

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

CVSS v3 metric

CVSS v3 base score 6.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L.

EPSS exploit prediction

EPSS: 0.002 (9.8th percentile), scored 2026-10-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 10th percentile — 9.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

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

Affected products

Weakness classification (CWE)

CWE-693 — Protection Mechanism Failure

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-2026-92039?: CVE-2026-92039 is a medium-severity vulnerability in Mozilla Firefox, classified under Protection Mechanism Failure. CVSS score: 6.3/10. Published 2026-09-15.
How severe is CVE-2026-92039?: Medium severity. CVSS v3 base score is 6.3 out of 10.