Microsoft to Phase Out Service Principal-Less Authentication in Entra ID

Microsoft has announced plans to retire service principal-less authentication for Entra ID customers by next year. Administrators are being urged to take proactive steps now to prepare their organizations for this upcoming change.

In Microsoft Entra ID, service principal-less authentication is a method where applications authenticate without having a dedicated service principal in the resource tenant. Without a service principal, applications can issue tokens without permissions and an object identifier (object ID). This approach can lead to incomplete validations and potential security vulnerabilities.

“This change to service principal-less authentication will make client service principal a requirement for all applications in order to improve our “Security by default.” Service principal-less authentication can be abused if the resource applications (i.e. APIs) perform incomplete validations,” Microsoft wrote in a support document.

Microsoft has confirmed that current validations for service principal-less authentication are secure. However, the company is taking proactive steps to minimize risks by ending support for this method. This move aims to prevent potential vulnerabilities from being exploited by third-party applications or reappearing in future versions.

Starting in March 2026, Microsoft will require all enterprise applications to be registered in each tenant where they authenticate. This change will give administrators greater control over resource access. For instance, they will be able to set specific policies that define the conditions under which applications can access organizational resources.

How to use sign-in logs to find service principal-less applications

Microsoft advises enterprise administrators to use sign-in logs to identify applications using service principal-less authentication. These apps can be found by locating sign-in entries with a specific service principal ID using the following steps:

• Log in to the Microsoft Entra admin center and navigate to Identity > Show more… > Monitoring & health > Sign-in logs.
• Click the “Service principal sign-ins” tab, filter by Service principal ID, and then type 00000000-0000-0000-0000-000000000000 in the input field.
• Change the date sorting option to a custom time interval and set it to “Last 1 month.”
• Select a log entry to view its details. In the side panel of the log details, navigate to the Application ID section and find the Client Application ID.

Finally, create an enterprise application in the resource tenant for each named application and register it using the Client App ID. Then, check the sign-in logs to ensure that the tokens issued to the application have a unique alphanumeric GUID as the Service principal ID.

Microsoft will handle the creation of service principals for their own apps, and IT admins only need to create service principals for third-party enterprise apps. Administrators should check their tenants for affected apps and contact the app owners to ensure they are prepared for the discontinuation of service principal-less authentication.