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.
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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
