What is CVE-2026-66311?

CVE-2026-66311 is a medium-severity vulnerability in Microsoft Edge Chromium, classified under Missing Authorization. CVSS score: 6.2/10. Published 2026-08-04.

How severe is CVE-2026-66311?

Medium severity. CVSS v3 base score is 6.2 out of 10.

Auth bypass in Microsoft Edge Chromium

CVE-2026-66311

Missing authorization in Microsoft Edge (Chromium-based) allows an unauthorized attacker to perform tampering locally.

Vulnerability class: Broken Access Control

EPSS: 0.003 (20.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.2 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

Affected products

Microsoft Edge_chromium
Microsoft Edge (Chromium-based) — versions 1.0.0.0

Weakness classification (CWE)

CWE-862 — Missing Authorization

References

Microsoft Edge (Chromium-based) Tampering Vulnerability (vendor-advisory, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2026-66311?: CVE-2026-66311 is a medium-severity vulnerability in Microsoft Edge Chromium, classified under Missing Authorization. CVSS score: 6.2/10. Published 2026-08-04.
How severe is CVE-2026-66311?: Medium severity. CVSS v3 base score is 6.2 out of 10.