All posts in category Network Device Enrollment Service

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

Certificate Connector for Microsoft Intune Agent Certificate Renewal Failure

The Certificate Connector for Microsoft Intune is a vital component that allows administrators to issue and manage enterprise PKI certificates to endpoints managed by Microsoft Intune. The connector is installed on a Windows server with access to the on-premises Certificate Authority (CA). It is registered with Intune and can be used by any PKCS or SCEP device configuration profiles defined by Intune administrators.

Agent Certificate

When you install the Certificate Connector for Intune, a certificate issued by the Microsoft Intune ImportPFX Connector CA is automatically enrolled into the local computer certificate store of the server where the connector is installed. This certificate authenticates the connector to Intune and is valid for one year from the date of issuance. This certificate is automatically renewed in most cases. However, some configurations prevent this from happening.

Failed To Renew

Administrators may find event log errors with event ID 2 from the CertificateConnectors source in the Microsoft-Intune-CertificateConnectors operational event log with the following information.

Pki Create Service:

Failed to renew agent certificate

System.Security.Cryptography.CryptographicException: Access is denied.

Root Cause

Agent certificate renewal fails when the Certificate Connector for Intune is running under a service account that is not a member of the local administrators security group. You will not encounter this error if the connector services are running in the SYSTEM context, however.

Resolution

There are a few different ways to resolve this issue. Here are some options to consider.

Grant Admin Rights

Adding the service account under which the connector service runs will allow the agent certificate to renew automatically. However, this may not be desirable from a security perspective. To address this, administrators may temporarily grant local administrative access to renew the agent certificate, then revoke this permission once the certificate has been successfully renewed. However, this is a manual process that doesn’t scale well and requires annual administrative intervention.

Reinstall

Uninstalling and reinstalling the Certificate Connector for Intune will force a new certificate enrollment during the registration process. You can delete the old certificate after completing the installation.

Switch to SYSTEM

Changing from a service account to SYSTEM will also resolve this issue. However, it is not recommended to make these changes directly on the services themselves. Instead, administrators should remove and reinstall the Certificate Connector for Intune, selecting the SYSTEM option rather than the service account method.

Note: Using the SYSTEM account for the Certificate Connector for Intune should be avoided when using PKCS. Details here.

Summary

The Certificate Connector for Intune agent certificate renewal fails when the service is configured to run as a service account without local administrative rights. The best way to resolve this is to add the service account to the local administrators group on the server where the connector is installed. However, this isn’t always ideal. Although running the connector in the SYSTEM context is acceptable when using SCEP, it should be avoided when using PKCS. Administrators will have to accept the risk of the service account having local administrative rights or accept that they’ll have to reinstall the connector annually.

Additional Information

Certificate Connector for Intune Service Account and PKCS

Strong Certificate Mapping for Intune PKCS and SCEP Certificates

Intune Strong Certificate Mapping Error

Intune PKCS and SCEP Certificate Validity Period

Certificate Connector for Intune Failure

Certificate Connector for Intune Configuration Failed

Troubleshooting Intune Failed PKCS Request

Intune PKCS and SCEP Certificate Validity Period

With the recent announcement of drastically reduced certificate lifetimes for public TLS certificates, there has been much discussion about certificate lifetimes for private certification authorities (CAs) like Microsoft Active Directory Certificate Services (AD CS). Most commonly, AD CS certificates are issued with a one-year validity period. However, as I’ve discussed in the past, there’s good reason to consider shorter lifetimes in many scenarios. Reducing certificate lifetimes is a growing trend to enhance security, but it poses challenges for private CAs like AD CS. This post explains how to manage shorter certificate lifetimes in Intune using PKCS and SCEP.

AD CS Template

With AD CS, the administrator defines the certificate lifetime by setting the validity period value when creating the certificate template in Active Directory (AD), as shown here.

All certificates issued using this template will be valid for one year from the date of issuance.

Note: The only exception would be if the issuing CA’s certificate were due to expire before the one-year expiration date. In that case, the certificate would be valid until the CA certificate expires.

Intune PKCS and SCEP

When issuing certificates with Intune using either PKCS or SCEP, administrators deploy an Intune enrollment certificate template in AD that Intune uses for user and device certificate enrollment. While the Intune enrollment certificate template defines the default validity period, Intune also allows administrators to specify a desired validity period in the PKCS or SCEP policy settings, as shown here.

Intune Validity Period and AD CS

Although Intune provides the ability to define the validity period on the PKCS or SCEP policy, AD CS does not honor this setting unless explicitly configured to do so. Instead, it defaults to the period defined in the certificate template. Using the example above, the administrator defined a validity period of 1 month. However, since the Intune enrollment certificate template’s validity period was set to one year, a certificate valid for one year will be issued.

Override Template Settings

Fortunately, there is a way to override this default behavior. On the issuing CA where the Intune enrollment certificate template is published, open an elevated PowerShell command window and run the following command.

certutil.exe -setreg Policy\EditFlags +EDITF_ATTRIBUTEENDDATE

Once complete, run the following PowerShell command to restart the CA service.

Restart-Service -Name CertSvc -PassThru

After making this change, administrators can define a shorter certificate validity period than specified on the template using Intune PKCS and SCEP policies.

Note: For security reasons, this setting only allows requests that are shorter than the template’s defined validity period. You cannot request a certificate with a validity period that is longer than the template allows.

Summary

By enabling the EDITF_ATTRIBUTEENDDATE flag on your issuing CA, you gain flexibility to tailor certificate validity periods per use case—while still enforcing a maximum validity via the AD Intune certificate enrollment template. Flexible certificate validity periods are especially valuable in environments that are moving toward short-lived certificates for improved security posture.

Additional Information

TLS Certificate Lifetimes Will Officially Reduce to 47 Days

Always On VPN SSTP and 47-Day TLS Certificates

The Case for Short-Lived Certificates in Enterprise Environments

Mastering Certificates with Microsoft Intune – Live Online Training

Richard M. Hicks Consulting, Inc.

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All posts in category Network Device Enrollment Service

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