ReviewHigh

CVE-2026-66808

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

Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.

PRIORITY ASSESSMENT

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability-

Technical severityCVSS 8.8

Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.

Product: Microsoft Microsoft SharePoint Enterprise Server 2016, Microsoft SharePoint Server 2019, Microsoft SharePoint Server Subscription Edition
Affected versions: >= 16.0.0 < 16.0.5565.1001, >= 16.0.0 < 16.0.10417.20198, >= 16.0.0 < 16.0.19725.20522, 2016, 2019
Fixed versions: Verify the fixed release separately for each affected product line

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.