What is CVE-2026-55040?

CVE-2026-55040 is a critical-severity vulnerability in Microsoft Sharepoint Enterprise Server 2016, classified under Weak Authentication. CVSS score: 9.1/10. Published 2026-07-14.

How severe is CVE-2026-55040?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Vulnerability in Microsoft Sharepoint Enterprise Server 2016

CVE-2026-55040

Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

Affected products

Microsoft Sharepoint Enterprise Server 2016 — versions 16.0.0
Microsoft Sharepoint Server 2019 — versions 16.0.0
Microsoft Sharepoint Server Subscription Edition — versions 16.0.0

Weakness classification (CWE)

CWE-1390 — Weak Authentication

References

secure@microsoft.com (vendor-advisory, patch)

Frequently asked questions

What is CVE-2026-55040?: CVE-2026-55040 is a critical-severity vulnerability in Microsoft Sharepoint Enterprise Server 2016, classified under Weak Authentication. CVSS score: 9.1/10. Published 2026-07-14.
How severe is CVE-2026-55040?: Critical severity. CVSS v3 base score is 9.1 out of 10.