CVE-2026-40357: Microsoft SharePoint Server Remote Code Execution Vulnerability

Overview

Severity
High (CVSS 8.8)
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Category
Remote Code Execution
Exploit Status
Not Exploited
Exploitation Likelihood
Less Likely
Patch Tuesday
2026-May
Released
2026-05-12
EPSS Score
0.50% (percentile: 66.2%)

Description

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

FAQ

According to the CVSS metric, privileges required is low (PR:L). What does that mean for this vulnerability? Any authenticated attacker could trigger this vulnerability. It does not require admin or other elevated privileges. I am running SharePoint Server 2016. Do the updates for SharePoint Enterprise Server 2016 also apply to the version I am running? Yes. The same KB number applies to both SharePoint Server 2016 and SharePoint Enterprise Server 2016. Customers running either version should install the security update to be protected from this vulnerability. How could an attacker exploit the vulnerability? In a network-based attack, an authenticated attacker, who has a minimum of Site Member permissions (PR:L), could execute code remotely on the SharePoint Server.

Affected Products (3)

Microsoft Office

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

Security Updates (3)

Acknowledgments

Oleksandr Mirosh

Revision History

  • 2026-05-12: Information published.