CVE-2026-55021: Microsoft SharePoint cross-site scripting vulnerability

CVE-2026-55021 · Severity: high · CVSS 7.3 · Published 2026-07-14

Microsoft SharePoint is a widely used collaboration and document management platform. A security vulnerability in this software could allow an attacker with basic user permissions to trick other users into performing unintended actions or revealing sensitive information. This type of attack, known as spoofing, can compromise the integrity of corporate data and lead to unauthorized access to internal resources.

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

Quick answers

Is CVE-2026-55021 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55021 being exploited in the wild.
How severe is CVE-2026-55021?
High severity, with a CVSS score of 7.3, published 14 July 2026.
Which products and versions are affected?
Microsoft SharePoint Enterprise Server 2016 < 16.0.5561.1001; Microsoft SharePoint Server 2019 < 16.0.10417.20175; Microsoft SharePoint Server Subscription Edition < 16.0.19725.20434.
Is there a fix for CVE-2026-55021?
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-2026-55021 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-55021?
Check whether you run Microsoft SharePoint Enterprise Server 2016, 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 cross-site scripting (XSS) vulnerability exists in Microsoft Office SharePoint due to improper neutralization of input during web page generation. An authenticated attacker with low-level privileges can exploit this flaw by sending a specially crafted request over the network. Successful exploitation requires user interaction, typically from a victim visiting a malicious or compromised page, and allows the attacker to perform spoofing and potentially gain unauthorized access to sensitive information. Microsoft has released security updates for SharePoint Enterprise Server 2016, SharePoint Server 2019, and SharePoint Server Subscription Edition to address this issue.

Affected products

  • Microsoft SharePoint Enterprise Server 2016 < 16.0.5561.1001
  • Microsoft SharePoint Server 2019 < 16.0.10417.20175
  • Microsoft SharePoint Server Subscription Edition < 16.0.19725.20434

Timeline

  • 2026-07-14: disclosed: Initial publication of CVE-2026-55021
  • 2026-07-14: advisory: Microsoft released security update guide details

References

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