CVE-2026-58644: Microsoft SharePoint Deserialization of Untrusted Data Vulnerability

Critical severity, CVSS 9.8. Actively exploited: in CISA KEV since 2026-07-16. EPSS: 15.9% chance of exploitation in the next 30 days.

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

Affected products

• Microsoft SharePoint Server: before 16.0.19725.20434 (fixed in 16.0.19725.20434); version 2016 only; version 2019 only

Published 2026-07-14. Last modified 2026-07-17.