Windows Server 2016 End of Life January 2027: Plan Your AD CS Migration Now

Happy New Year, everyone! As the calendar rolls over to 2026, it’s time to start planning the migration of workloads hosted on Windows Server 2016. Mainstream support ended for Windows Server 2016 on January 11, 2022, after which it entered extended support. However, extended support for Windows Server 2016 ends on January 12, 2027, at which point it will be end of life and no longer supported. Running production workloads on Windows Server 2016 beyond this date exposes organizations to significant security risk, as it no longer receives security updates, leaving these systems vulnerable to exploits.

Active Directory Certificate Services

Many organizations are still running critical infrastructure on Windows Server 2016. Administrators often delay upgrading Microsoft Active Directory Certificate Services (AD CS) due to its complexity. However, a well-planned AD CS migration not only reduces risk but also provides an opportunity to modernize cryptography, certificate templates, and operational practices.

Certificate Authorities

Administrators must carefully migrate Certificate Authorities (CAs) running on Windows Server 2016 to minimize downtime. In environments where ongoing CA maintenance has been limited, migrating the CA database can be especially challenging. If the CA is installed on a domain controller, now is a good time to consider separating these services to ensure reliable operation. Also, it’s a good idea to evaluate the CA’s configuration and security posture during migration to enhance security and improve service resilience.

NDES Servers

Microsoft Network Device Enrollment Services (NDES) servers, commonly deployed to facilitate certificate enrollment via Microsoft Intune, pose a unique challenge during migration. Unfortunately, configuring NDES is exceedingly complex and error-prone. NDES relies on a delicate combination of specialized IIS configuration, AD service accounts, custom certificate templates, and CA permissions, making even minor changes risky without proper planning. Not surprisingly, administrators are often hesitant to touch these systems as they are notoriously difficult to troubleshoot when problems arise.

Pro Tip: We spend an entire day covering NDES configuration in the Mastering Enterprise PKI Certificates with Microsoft Intune training course. The next session is March 10-12, 2026. Register now!

Intune Certificate Connectors

Don’t overlook Windows Server 2016 servers with the Intune Certificate Connector installed. Fortunately, this is one of the more manageable workloads to migrate. All that’s required is to install new connectors on supported servers and delete the old ones.

Summary

With extended support for Windows Server 2016 ending on January 12, 2027, organizations running production workloads—especially critical infrastructure such as Active Directory Certificate Services (AD CS), Certificate Authorities (CAs), and NDES servers—face significant security risks from unpatched vulnerabilities once the OS reaches end-of-life. Careful migration planning to newer versions such as Windows Server 2022 or 2025 is essential to minimize downtime, improve security posture, and ensure long-term resilience.

Start Planning Now

Don’t leave these mission-critical infrastructure services to the last minute! Begin planning your migration today. If you’d like expert guidance, I have many years of experience migrating these workloads. I have developed specialized tools and techniques to ensure a smooth, secure, and successful transition. Fill out the form below to schedule a free one-hour consultation to assess your Windows Server 2016 AD CS workloads, identify migration risks, and outline next steps.

Additional Information

Windows Server 2016 Lifecycle Policy

PKI Fundamentals with Microsoft Active Directory Certificate Services (AD CS) Online Training Course

Mastering Enterprise PKI Certificates with Microsoft Intune Online Training Course

Resolving PKCS Certificate Mapping Issues in Windows Autopilot Hybrid Join Deployments

Microsoft Windows Autopilot streamlines device provisioning through Intune, allowing IT administrators to preconfigure new Windows devices with minimal hands-on effort. However, when combined with Hybrid Entra Join and PKCS certificate deployment, specific challenges arise—particularly with certificate mapping and authentication.

Hybrid Entra Join

During autopilot provisioning, administrators may also choose to join the device to their on-premises Active Directory domain, a deployment model called Hybrid Entra join. Hybrid Entra join presents some unique challenges when using Autopilot to remotely provision devices. Specifically, the user must have connectivity to a domain controller to perform the first logon, as they do not have a user profile on the endpoint.

Device Tunnel

To support offline Hybrid Entra join during Autopilot provisioning, administrators can deploy the Always On VPN device tunnel to provide pre-logon connectivity to domain controllers. A device tunnel connection enables users to log on to their newly provisioned device remotely.

Requirements

The following prerequisites must be met to support the Always On VPN device tunnel.

  • The endpoint must be running Windows Enterprise edition.
  • An Always On VPN device tunnel profile must be assigned to the device.
  • A machine certificate must be deployed to the endpoint that includes the Client Authentication EKU (OID 1.3.6.1.5.5.7.3.2).

Note: If you plan to use the subscription step-up upgrade from Windows Professional to Windows Enterprise, the device tunnel will not connect automatically after provisioning is complete, which prevents the user from logging in. More details and a workaround for this issue can be found here.

Strong Certificate Mapping

Microsoft knowledge base article KB5014754, released in May of 2022, introduced changes to domain controllers to require strong certificate mapping when using certificates to authenticate to Active Directory (AD). It was initially deployed in compatibility mode, only warning administrators when certificates are used for authentication that aren’t strongly mapped. However, full enforcement is mandatory beginning with the September 2025 security updates. This requirement introduces some challenges when issuing certificates to the device using PKCS during Autopilot provisioning.

Intune PKCS Certificates

When using PKCS certificates and the Intune Certificate Connector, the endpoint’s on-premises AD security identifier (SID) is not added to the issued certificate during Autopilot. Interestingly, this does not happen when using SCEP certificates. If the device certificate is not strongly mapped, the Always On VPN device tunnel will still authenticate successfully because Always On VPN does not use AD to authenticate device connections. Instead, Always On VPN simply verifies the certificate (e.g., that it is not expired or revoked) and allows authentication if the certificate passes the validation.

However, enterprise Wi-Fi access may fail without strongly mapped certificates if device authentication is required. Also, there may be other scenarios where a device authentication certificate without strong mapping may cause authentication to fail.

Workarounds

There are a few ways to work around this limitation. Consider the following options.

Native Entra ID Join

The simplest way to avoid the challenges of PKCS certificates and Hybrid Entra join is to avoid it altogether in favor of native Entra join. However, this may not be an option for everyone.

Use SCEP

For some reason, certificates issued with SCEP do not suffer from this limitation. In my testing, SCEP certificates are always strongly mapped. However, deploying SCEP certificates is much more complex than using PKCS. (Pro tip: Cloud PKI for Intune uses SCEP and requires no configuration! It’s definitely something to consider.)

Short-Lived Certificates

Another option is to deploy temporary, short-lived certificates (valid for only a few days) using PKCS to ensure the Always On VPN device tunnel works, and then deploy a permanent, long-term certificate post-deployment that includes the strong mapping. To do this, administrators can leverage dynamic group assignments in Intune. For example, the administrator can assign the short-lived certificate to an Autopilot Provisioning devices group and later assign a long-term certificate to the Hybrid Joined devices group.

Here’s an example of the dynamic group membership configuration.

Autopilot Provisioning Devices:

(device.devicePhysicalIDs -any (_ -contains “[ZTDId]”)) -and (device.deviceTrustType -ne “ServerAD”)

Hybrid Entra Join Devices:

(device.deviceTrustType -eq “ServerAD”)

In this configuration, the initial PKCS certificate is deployed without the strong mapping when the endpoint is enrolled to Autopilot but has not yet joined the domain. During this time, the endpoint will only be a member of the Autopilot Provisioning Devices group and will receive the short-lived, temporary certificate. Later, once the endpoint has successfully joined the domain, the device will move from the provisioning group to the Hybrid Entra Join Devices group. When this happens, a permanent, strongly mapped long-term certificate is enrolled on the device.

Manual Certificate Mapping

Certificates can be manually mapped via the altSecurityIdentities property of the computer object in AD. Obviously, this doesn’t scale well, so my good friend Steve Prentice published a PowerShell script to automate this process. You can find more details and the script here.

Summary

Windows Autopilot streamlines device provisioning with Intune, but Hybrid Entra Join introduces challenges when PKCS certificates lack strong mapping during initial deployment, potentially disrupting VPN and Wi-Fi authentication. Administrators can avoid this by switching to native Entra join or by using workarounds such as switching to SCEP, using short-lived certificates, or manually mapping certificates.

Additional Information

KB5014754 – Certificate-based authentication changes on Windows domain controllers

How To: Map a user to a certificate via all methods available in the altSecurityIdentities attribute

Hybrid Autopilot: Automating altSecurityIdentities

Configure Microsoft Entra hybrid join

Overview: Cloud PKI for Microsoft Intune

PKI Fundamentals with Microsoft AD CS Training Course

I’m excited to announce that I’ve partnered once again with the fine folks at the ViaMonstra Online Academy to deliver a new live training course entitled PKI Fundamentals with Microsoft Active Directory Certificate Services (AD CS). The event consists of six weekly live webinars beginning on Thursday, January 15, 2026, at 3:00 PM CST.

Why AD CS Training?

Digital certificates are strong, phishing-resistant credentials that are an excellent choice for authentication to critical workloads like Always On VPN and enterprise Wi-Fi. However, managing certificate services infrastructure can be daunting. This course provides administrators with a fundamental understanding of enterprise PKI with Microsoft AD CS.

Course Overview

The event format for this course consists of six weekly live sessions on Thursdays starting on January 15, 2026. The classes are two hours long, running from 3:00 PM CST to 5:00 PM CST each day. During the course, we’ll cover the following topics.

  • PKI concepts and certificate use cases
  • Designing and deploying certificate authorities (CAs)
  • Configuring templates and enrollment
  • Managing revocation and maintenance

Who Should Attend

Organizations planning to use certificate authentication for enterprise VPN and Wi-Fi workloads will benefit from this training course. Also, those considering a new AD CS deployment will find this training beneficial. In addition, administrators managing an existing production AD CS environment will gain valuable insight.

Enroll Now

Registration for this training class is available now. The cost is $295.00—an incredible bargain! Don’t miss out on this fantastic opportunity to gain foundational AD CS skills. Click the registration link below and reserve your spot today!

Additional Information

Public Key Infrastructure (PKI)

Enterprise PKI

Cloud PKI for Microsoft Intune