CVE-2026-40368: Microsoft SharePoint deserialization of untrusted data

CVE-2026-40368 · Severity: high · CVSS 8 · Published 2026-05-12

Microsoft SharePoint, a widely used platform for document management and team collaboration, is affected by a security vulnerability that could allow an authorized user to execute malicious code on the server. An attacker with basic user permissions could exploit this flaw to gain full control over the SharePoint environment, potentially leading to the theft of sensitive corporate data or disruption of business operations. Organizations should apply the available security updates from Microsoft to protect their internal document repositories.

Technologies: Microsoft SharePoint Server 2016 Enterprise Edition, Microsoft SharePoint Server 2019, Microsoft SharePoint Server Subscription Edition. Vendors: Microsoft.

Quick answers

Is CVE-2026-40368 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-40368 being exploited in the wild.
How severe is CVE-2026-40368?
High severity, with a CVSS score of 8, published 12 May 2026.
Which products and versions are affected?
Microsoft SharePoint Server Subscription Edition up to (excluding) 16.0.19725.20280.
Is there a fix for CVE-2026-40368?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-40368 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-40368?
Check whether you run Microsoft SharePoint Server 2016 Enterprise Edition, Microsoft SharePoint Server 2019 or Microsoft SharePoint Server Subscription Edition at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A deserialization vulnerability (CWE-502) exists in Microsoft SharePoint Server due to the improper handling of untrusted data. An attacker with Site Member permissions (low privilege) can exploit this by sending a specially crafted request to a vulnerable SharePoint instance. Successful exploitation requires some user interaction and allows the attacker to achieve remote code execution (RCE) in the context of the SharePoint service account. The vulnerability affects SharePoint Server 2016, 2019, and Subscription Edition; Microsoft has released security updates to address this issue.

Affected products

  • Microsoft SharePoint Server 2016 Enterprise Edition
  • Microsoft SharePoint Server 2019
  • Microsoft SharePoint Server Subscription Edition up to (excluding) 16.0.19725.20280

Timeline

  • 2026-05-12: disclosed
  • 2026-05-12: advisory: MSRC advisory published

References

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