CVE-2026-20963: Microsoft SharePoint deserialization of untrusted data

CVE-2026-20963 · Severity: critical · CVSS 9.8 · Exploited in the wild · Published 2026-03-18

Microsoft SharePoint, a widely used platform for document management and team collaboration, contains a critical security flaw. This vulnerability allows an unauthenticated attacker to remotely take control of the server over the network. Successful exploitation could lead to the theft of sensitive corporate data, complete service disruption, or a foothold for further attacks within the organization's internal network. This flaw is reportedly being actively exploited in the wild.

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

Quick answers

Is CVE-2026-20963 exploited in the wild?
Yes. CVE-2026-20963 is known to be exploited in the wild, first recorded on 18 March 2026. Treat it as urgent.
How severe is CVE-2026-20963?
Critical severity, with a CVSS score of 9.8, published 18 March 2026.
Which products and versions are affected?
Microsoft SharePoint Server Subscription Edition up to (excluding) 16.0.19127.20442.
Is there a fix for CVE-2026-20963?
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-2026-20963 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-20963?
Check whether you run Microsoft SharePoint, Microsoft SharePoint Server 2016 Enterprise Edition, Microsoft SharePoint Server 2019 or one of the others listed 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 critical deserialization vulnerability (CWE-502) exists in Microsoft SharePoint Server. The flaw stems from the improper handling of untrusted data during deserialization, which allows an attacker to bypass security checks and execute arbitrary code. The attack vector is network-based and requires no prior authentication or user interaction (AV:N/AC:L/PR:N/UI:N). Attackers can achieve full system compromise of the affected SharePoint instance. Microsoft has released security updates to address this issue, and CISA has added this vulnerability to its Known Exploited Vulnerabilities (KEV) catalog.

Affected products

  • Microsoft SharePoint Server 2016 Enterprise Edition
  • Microsoft SharePoint Server 2019
  • Microsoft SharePoint Server Subscription Edition up to (excluding) 16.0.19127.20442

Timeline

  • 2026-01-13: disclosed: Initial disclosure by Microsoft Corporation
  • 2026-03-18: kev added: Added to CISA Known Exploited Vulnerabilities catalog
  • 2026-03-18: exploited: Confirmed active exploitation in the wild
  • 2026-04-01: advisory: NVD entry updated with revised CVSS and description details

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