CVE-2026-56164 in Microsoft SharePoint Server
Microsoft SharePoint contains a missing authentication for critical function vulnerability that allows an unauthorized attacker to elevate privileges over a 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
- SharePoint Enterprise Server 2016 before 16.0.5561.1001
- SharePoint Server 2019 before 16.0.10417.20175
- SharePoint Server Subscription Edition before 16.0.19725.20434
Fixed versions
- SharePoint Enterprise Server 2016 16.0.5561.1001 or later
- SharePoint Server 2019 16.0.10417.20175 or later
- SharePoint Server Subscription Edition 16.0.19725.20434 or later
How to fix it
CVE-2026-56164 affects Microsoft SharePoint Server. In simple terms, a person without the right login may reach a protected action. Fix it by updating to SharePoint Enterprise Server 2016 16.0.5561.1001 or later; SharePoint Server 2019 16.0.10417.20175 or later; SharePoint Server Subscription Edition 16.0.19725.20434 or later. If this system is online or used by admins, treat the fix as urgent.
- Find every place where Microsoft SharePoint Server is installed or used.
- Check if the version matches: SharePoint Enterprise Server 2016 before 16.0.5561.1001; SharePoint Server 2019 before 16.0.10417.20175; SharePoint Server Subscription Edition before 16.0.19725.20434.
- Update or apply the vendor fix: SharePoint Enterprise Server 2016 16.0.5561.1001 or later; SharePoint Server 2019 16.0.10417.20175 or later; SharePoint Server Subscription Edition 16.0.19725.20434 or later.
- If you cannot update today, allow only trusted users and trusted networks.
- Turn off the affected feature or plugin if the vendor says that is safe to do.
- Check logs for crashes, strange requests, new admin actions, or unexpected access.
- Change secrets or passwords if you think data or admin access may have been exposed.
Scan now. Google sign-in is only needed to unlock fix guidance.
Verify the fix
- Confirm the installed version or mitigation matches: SharePoint Enterprise Server 2016 16.0.5561.1001 or later; SharePoint Server 2019 16.0.10417.20175 or later; SharePoint Server Subscription Edition 16.0.19725.20434 or later.
- Confirm the affected feature is no longer exposed to untrusted users.
- Run the affected workflow again and make sure it still works.
- Review logs again after the fix for repeated suspicious activity.
- Run a new Fixnx scan if this software is part of a public website.
- Save the advisory link and proof of the fix in your change record.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-56164?
Microsoft SharePoint Server versions listed as affected should be reviewed: SharePoint Enterprise Server 2016 before 16.0.5561.1001, SharePoint Server 2019 before 16.0.10417.20175, SharePoint Server Subscription Edition before 16.0.19725.20434.
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.