Strong Certificate Mapping Enforcement February 2025

Are you ready? In just a few short weeks(!) Microsoft will release the February 2025 security updates. This is a critical update because Microsoft plans to enable full enforcement of strong certificate mapping on Active Directory Domain Controllers (DCs) with this release. Administrators unprepared for this may incur outages for workloads using certificate-based authentication such as Always On VPN, Wi-Fi, and others.

Reminder: There’s still space available in my Certificates and Intune Masterclass. Register now!

KB5014754

Microsoft introduced strong certificate mapping with the May 2022 update KB5014754 to address vulnerabilities identified with certificate-based authentication. The update makes changes to Active Directory Certificate Services (AD CS) certification authorities (CAs) to embed the principal’s Security Identifier (SID) on issued certificates with a new certificate extension. The update also changes domain controller behavior to monitor and optionally enforce strong certificate mapping for authentication.

Enforcement Mode

When first introduced, the update is configured in compatibility mode. If a certificate that isn’t strongly mapped is presented for authentication, an event is recorded in the event log indicating that. Microsoft has been planning for years to enable full enforcement. After many delays, that time is now upon us. Specifically, full enforcement for strong certificate mapping will be enabled by default on DCs after applying the February 2025 security updates.

Note: Administrators can switch back to compatibility mode for now. See below for more details.

Limitations

Initially, the strong certificate mapping update was applied only to online certificate templates. Specifically, those templates are configured to build the subject name from Active Directory information. However, offline templates, where the subject name is supplied in the request, do not include this information by default. Crucially, any certificate issued with Microsoft Intune with PKCS or SCEP uses offline templates and is not strongly mapped. The lack of strong certificate mapping options for Intune-issued certificates forced Microsoft to delay its full enforcement deadline until these limitations were resolved.

Updates

In October 2024, Microsoft Intune announced support for strong certificate mapping for PKCS and SCEP certificates. Administrators can now configure these certificates to include strong certificate mapping. However, administrators must take action to affect this change.

PKCS

To enable strong certificate mapping for PKCS certificates, administrators must ensure that the certificate connector is running at least version 6.2406.0.1001. In addition, the following registry key must be configured on the connector server.

Key: HKLM\Software\Microsoft\MicrosoftIntune\PFXCertificateConnector
Name: EnableSidSecurityExtension
Type: DWORD
Value: 1

You can implement this change by opening an elevated PowerShell command window and running the following command.

Set-ItemProperty -Path ‘HKLM:\SOFTWARE\Microsoft\MicrosoftIntune\PFXCertificateConnector’ -Name EnableSidSecurityExtension -Value 1 -Force

The Intune Certificate Connector server must be restarted for this change to take effect. No changes are required on the PKCS certificate policy in Intune.

SCEP

To enable strong certificate mapping for SCEP certificates, administrators must add the following attribute/value pair to the Subject alternative name settings on their existing Intune SCEP certificate policy.

Attribute: URI
Value: {{OnPremisesSecurityIdentifier}}

Preparation

Administrators using certificate-based authentication against on-premises Active Directory should ensure all user and device authentication certificates include embedded SID information. For certificates issued on-premises, with Intune using PKCS or certificates issued by Entra Conditional Access, the certificate should now have the extension 1.3.6.1.4.1.311.25.2, including the principal’s SID.


SCEP certificates issued using Intune will include the following information in the Subject Alternative Name field.

URL=tag:microsoft.com,2022-09-24:sid:<sid>


Note: This applies to certificates issued using Cloud PKI for Microsoft Intune as those certificates are deployed using a SCEP device configuration policy.

Opt-Out

With the February 2025 security update, all domain controllers will be switched to full enforcement mode. Authentication requests using certificates without strong mapping will be denied in this configuration.

If your organization is not prepared to move to full enforcement mode, the February 2025 update allows administrators to opt out and switch back to compatibility mode by enabling the following registry key on all domain controllers.

Key: HKLM:\SYSTEM\CurrentControlSet\Services\Kdc
Name: StrongCertificateBindingEnforcement
Type: DWORD
Value: 1

You can implement this change by opening an elevated PowerShell command window and running the following command.

New-ItemProperty -Path ‘HKLM:\SYSTEM\CurrentControlSet\Services\Kdc’ -Name ‘StrongCertificateBindingEnforcement’ -PropertyType DWORD -Value 1 -Force

September 2025

Administrators are strongly encouraged to update all user and device authentication certificates before September 2025. With the September 2025 security update, Microsoft will no longer honor the opt-out registry settings and strictly enforce strong certificate mapping for all certificate-based authentication requests.

Troubleshooting

Certificate authentication is commonly used for Always On VPN and Wi-Fi authentication. If full enforcement mode is enabled on domain controllers and a certificate is presented for authentication that is not strongly mapped, administrators may see the following event log information recorded on the Network Policy Server (NPS).

Network Policy Server denied access to a user.

The details of the event include the following.

Reason Code: 16
Reason: Authentication failed due to a user credentials mismatch. Either the user name provided does not map to an existing user account or the password was incorrect.

Obviously, the user does not enter their password when using certificates for authentication. However, the indication of a credential mismatch can be caused by missing strong certificate mapping information when the DC is in full enforcement mode.

Note: There are other causes for reason code 16 failures on NPS. Further investigation may be required to determine the root cause.

Additional Information

Training: Certificates and Intune Masterclass

Certificate-Based Authentication Changes and Always On VPN

Strong Certificate Mapping for Intune PKCS and SCEP Certificates

Entra Conditional Access Certificates with SID Information Now Available

Intune Strong Certificate Mapping Error

Strong Certificate Mapping Error with PKCS

KB5014754: Certificate-Based Authentication Changes on Windows Domain Controllers

Free Entra Certificate-Based Authentication Training Course

I’m pleased to announce I’ll present a FREE online training course on Microsoft Entra Certificate-Based Authentication (CBA). The course will be delivered through the ViaMonstra Online Academy on Wednesday, November 6, beginning at 10:00 AM CST. Once again, this training course is entirely FREE, so don’t hesitate to register now! If you can’t attend the live session, you can always view the presentation recording later.

Course Highlights

Join me for this 90-minute live, online training session where you will learn:

  • How certificate-based authentication offers more robust protection than passwords alone and mitigates phishing and MFA bypass risks
  • How Entra CBA enables a seamless, passwordless user experience while maintaining high security and assurance
  • How Entra CBA eliminates the need for physical authentication devices such as FIDO keys or security tokens, reducing costs and complexity
  • How to configure and manage affinity binding and authentication strength policies for Entra CBA

When you attend the live event, you’ll have the opportunity to ask questions directly during the presentation, so be sure to register today and join us for this free training session!

Additional Information

Mini-Course – Microsoft Entra Certificate-Based Authentication

Microsoft Security Service Edge Now Generally Available

A few weeks ago, Microsoft announced the general availability of its Security Service Edge (SSE) offering, Global Secure Access (GSA). GSA encompasses Entra Internet Access, a cloud-based Secure Web Gateway, and Entra Private Access, a Zero Trust Network Access (ZTNA) solution for accessing private data and applications on-premises.

ZTNA vs. VPN

Entra Private Access will be a compelling alternative to traditional VPN solutions such as Windows Always On VPN. Where traditional VPNs grant the endpoint an IP address on the internal network, Entra Private Access provides more granular access and does not require the device to be directly connected to the network.

GSA Client

Administrators must install the GSA client on all endpoints using Entra Internet Access or Entra Private Access. Today, the client is available for Windows and Android devices. iOS and macOS clients are forthcoming.

Private Network Connector

The Entra Private Access solution relies on the Entra Private Network Connector. The Entra Private Network Connector is a software component installed on-premises that provides remote access connectivity. Previously, it was called the Azure AD Application Proxy. Essentially, it is the same technology extended to support TCP and UDP network access in addition to HTTP.

Limitations

Entra Private Access is the way of the future for secure remote access. However, today, there are still some important limitations associated with this technology.

Private DNS

Although Microsoft announced general availability for Entra Private Access, it still lacks the private DNS feature many organizations require to provide feature parity with their existing VPN. This feature is still in private preview at the time of this writing. Hopefully, Microsoft will release this feature soon.

Device Connection

Entra Private Access does not support device-based connections. This limits its capabilities for domain-joined devices. If your organization uses hybrid Entra join today, consider sticking with Always On VPN until you move to native Entra joined endpoints.

Licensing

Global Secure Access (Entra Private Access and Entra Internet Access) are included in the Microsoft Entra Suite license. More information about Entra licensing can be found here.

Additional Information

Microsoft Global Secure Access Now Generally Available

Microsoft Entra Global Secure Access (GSA) Overview

Microsoft Entra Security Service Edge (SSE) on the RunAs Radio Podcast

Microsoft Entra Plans & Pricing