What is CVE-2026-40379?

CVE-2026-40379 is a critical-severity vulnerability in Microsoft Entra Id, classified under Information Disclosure. CVSS score: 9.3/10. Published 2026-05-12.

How severe is CVE-2026-40379?

Critical severity. CVSS v3 base score is 9.3 out of 10.

Information disclosure in Microsoft Entra Id

CVE-2026-40379

Exposure of sensitive information to an unauthorized actor in Azure Entra ID allows an unauthorized attacker to perform spoofing over a network.

Vulnerability class: Information Disclosure

Published 2026-05-12 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.3 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.009 (60.8th percentile), scored 2026-10-24.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 61st percentile — 60.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-200 — Information Disclosure

References

Azure Entra ID Spoofing Vulnerability (vendor-advisory, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2026-40379?: CVE-2026-40379 is a critical-severity vulnerability in Microsoft Entra Id, classified under Information Disclosure. CVSS score: 9.3/10. Published 2026-05-12.
How severe is CVE-2026-40379?: Critical severity. CVSS v3 base score is 9.3 out of 10.