CVE-2026-55020 in Microsoft SharePoint Server
Microsoft SharePoint Server has a cross-site scripting issue that can let an authorized attacker spoof content over the network.
Quick answer
Microsoft SharePoint Server should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- Microsoft SharePoint Enterprise Server 2016
- Microsoft SharePoint Server 2019
- Microsoft SharePoint Server Subscription Edition where listed by Microsoft
Fixed versions
- Apply the July 2026 Microsoft SharePoint Server security update for your installed SharePoint branch
How to fix it
Install the July 2026 SharePoint security update. The old server can let an attacker spoof content or gain more access.
- Back up the SharePoint farm and databases.
- Install the July 2026 security update for the installed SharePoint branch.
- Run the SharePoint configuration wizard if Microsoft requires it.
- Review recent logins, pages, and admin changes.
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Verify the fix
- Confirm the SharePoint build includes the July 2026 security update.
- Run the vulnerability scan again and confirm this CVE is gone.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-55020?
Microsoft SharePoint Server versions listed as affected should be reviewed: Microsoft SharePoint Enterprise Server 2016, Microsoft SharePoint Server 2019, Microsoft SharePoint Server Subscription Edition where listed by Microsoft.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.