CVE-2026-33112: Microsoft SharePoint deserialization of untrusted data

CVE-2026-33112 · Severity: high · CVSS 8.8 · Published 2026-05-12

Microsoft SharePoint, a widely used platform for document management and team collaboration, contains a security flaw that could allow an authorized user to take control of the server. By sending specially crafted data to the system, an attacker with basic user permissions can execute unauthorized commands. This could lead to the theft of sensitive corporate data, disruption of business operations, or further compromise of the internal network.

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

Quick answers

Is CVE-2026-33112 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-33112 being exploited in the wild.
How severe is CVE-2026-33112?
High severity, with a CVSS score of 8.8, 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-2026-33112?
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-2026-33112 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-33112?
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 must be authenticated to the SharePoint environment with at least low-privileged user permissions to exploit this flaw. By sending a specially crafted network request containing serialized objects, the attacker can trigger the execution of arbitrary code in the context of the SharePoint service account. This vulnerability affects SharePoint Server 2016, 2019, and Subscription Edition. Microsoft has released security updates to address this issue by improving how SharePoint validates serialized data.

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: Microsoft released the security update guide for this vulnerability.

References

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