Review reviewCritical

CVE-2026-55040

Microsoft Microsoft SharePoint Enterprise Server 2016, Microsoft SharePoint Server 2019, Microsoft SharePoint Server Subscription Edition

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

PRIORITY ASSESSMENT

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability1.35%

Technical severityCVSS 9.1

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

Product: Microsoft Microsoft SharePoint Enterprise Server 2016, Microsoft SharePoint Server 2019, Microsoft SharePoint Server Subscription Edition
Affected versions: >= 16.0.0 < 16.0.5561.1001, >= 16.0.0 < 16.0.10417.20175, >= 16.0.0 < 16.0.19725.20434, < 16.0.19725.20434, 2016, 2019
Fixed versions: 16.0.19725.20434

Confirm exposure before applying a vendor-supported change.

1
Identify
Confirm that Microsoft Microsoft SharePoint Enterprise Server 2016, Microsoft SharePoint Server 2019, Microsoft SharePoint Server Subscription Edition and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.