CVE-2025-53770: Microsoft SharePoint Deserialization of Untrusted Data Vulnerability

Critical severity, CVSS 9.8. Actively exploited: in CISA KEV since 2025-07-20. EPSS: 100% chance of exploitation in the next 30 days.

Deserialization of untrusted data in on-premises Microsoft SharePoint Server allows an unauthorized attacker to execute code over a network. Microsoft is aware that an exploit for CVE-2025-53770 exists in the wild. Microsoft is preparing and fully testing a comprehensive update to address this vulnerability. In the meantime, please make sure that the mitigation provided in this CVE documentation is in place so that you are protected from exploitation.

Affected products

• Microsoft SharePoint Server: before 16.0.18526.20508 (fixed in 16.0.18526.20508); version 2016 only; version 2019 only

Published 2025-07-20. Last modified 2026-08-04.