Windows Server January 2026 Updates: KB5073379, KB5073457, KB5073723
Microsoft's monthly Patch Tuesday rollups for Windows Server land with security and reliability fixes across supported releases.
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Key takeaways
- Microsoft issued three Windows Server cumulative updates for January 2026: KB5073379, KB5073457, and KB5073723.
- Each KB corresponds to a specific Windows Server release; administrators should confirm which applies to their environment.
- The updates are available via Windows Update, WSUS, and the Microsoft Update Catalog.
- As with all cumulative updates, test in a staging or pilot ring before deploying to production servers.
What to do now
Medium urgency- Map each server to the correct KB and review known issues
- Stage the update in a pilot ring before production deployment
- Schedule maintenance windows to accommodate required reboots
Microsoft has released its January 2026 cumulative updates for Windows Server, distributed under the knowledge base identifiers KB5073379, KB5073457, and KB5073723. The updates are delivered through Windows Update, WSUS, and the Microsoft Update Catalog as part of the monthly Patch Tuesday cycle.
For sysadmins and MSPs, these rollups are a standing part of the monthly patch cadence: each package maps to a specific Windows Server release and combines security fixes with quality improvements that should be validated before broad deployment.
Microsoft's January 2026 Windows Server cumulative updates ship as KB5073379, KB5073457, and KB5073723.
Review the KB that applies to your Windows Server release, check for known issues, and stage the update before rolling it out to production.
Affected & context
Microsoft released the January 2026 cumulative updates for Windows Server, tracked under KB5073379, KB5073457, and KB5073723.
Windows Server underpins Active Directory, file services, and application hosting in enterprise environments, so the monthly cumulative updates are a routine but important part of patch management.
Organizations running supported Windows Server releases covered by the January 2026 cumulative updates.
- Vendors
- Microsoft
- Products
- Windows Server
- Geography
- Global
What Microsoft released
Microsoft has published its January 2026 cumulative updates for Windows Server, identified by three separate knowledge base numbers: KB5073379, KB5073457, and KB5073723. Each package targets a specific supported Windows Server release and rolls up the month's security and quality fixes into a single installable update.
The updates reach servers through the usual channels — Windows Update, Windows Server Update Services (WSUS), and the Microsoft Update Catalog for manual or offline deployment. Administrators managing multiple server versions may need to deploy more than one of these KBs depending on the mix of releases in their estate.
Confirm your build
Because cumulative updates are release-specific, verify the current OS build of each server before selecting a KB. Applying the wrong package will simply not install, but confirming ahead of time avoids wasted maintenance windows.
Who should act
These updates are relevant to any organization running a supported Windows Server release covered by the January 2026 servicing cycle. That typically includes domain controllers, file and print servers, application hosts, and Hyper-V infrastructure.
- IT administrators managing on-premises Windows Server fleets
- Managed service providers patching customer environments
- Teams running Windows Server as domain controllers or core infrastructure
Deployment guidance
- Identify the Windows Server release running on each server and map it to the correct KB (KB5073379, KB5073457, or KB5073723).
- Review Microsoft's release notes for each applicable KB to check for known issues before deployment.
- Deploy to a pilot or staging ring first and validate critical workloads such as Active Directory, DNS, and line-of-business applications.
- Schedule a maintenance window for production rollout, accounting for the reboot that cumulative updates require.
Test before production
Cumulative updates occasionally introduce regressions on specific configurations. Staging the rollout protects production servers from unexpected behavior.
Impact
The January 2026 cumulative updates deliver routine security and quality fixes that administrators must schedule and test as part of monthly patch management.
Business impact
Deploying the updates requires maintenance windows and server reboots, which must be coordinated to minimize service disruption.
Technical impact
Cumulative updates modify OS build numbers and may require a restart to complete installation.
Security impact
The updates include security fixes; delaying deployment leaves servers exposed to any patched vulnerabilities.
Affected audience: IT administrators, Managed service providers
Action required.
Response
Customer guidance
Microsoft distributes the updates through Windows Update, WSUS, and the Microsoft Update Catalog; administrators should apply the KB matching their Windows Server release.
Response status: Patched
Patch available: Yes
Workaround available: No
FAQ
Which Windows Server updates were released in January 2026?
Microsoft released three cumulative updates for Windows Server in January 2026: KB5073379, KB5073457, and KB5073723. Each targets a specific supported Windows Server release.
How do I install these Windows Server updates?
The updates are available through Windows Update, WSUS, and the Microsoft Update Catalog. Apply the KB that matches your server's Windows Server release, and expect a reboot to complete installation.
Should I deploy the updates immediately?
Because they include security fixes, deploy promptly — but test in a pilot or staging ring first to catch any regressions before rolling out to production servers.
The bottom line
Microsoft's January 2026 Patch Tuesday brought three Windows Server cumulative updates — KB5073379, KB5073457, and KB5073723 — with security and quality fixes for supported releases.
Treat these updates as part of routine patch management: confirm the build, test, then deploy within your maintenance window.
What happens next
Administrators should identify the applicable KB for each server, review known issues, and deploy after pilot testing. The next monthly cumulative update will follow in the February Patch Tuesday cycle.
What to do
Review the KB that applies to your Windows Server release and schedule deployment.
Sources
Anavem
Claims supported
- Microsoft released Windows Server January 2026 updates KB5073379, KB5073457, and KB5073723.
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