Error - AADSTS75011 Authentication method by which the user authenticated with the service doesn't match requested authentication method AuthnContextClassRef

This article describes a problem in which you receive the error message "Error - AADSTS75011 Authentication method by which the user authenticated with the service doesn't match requested authentication method AuthnContextClassRef." when trying to sign into a SAML-based single sign-on (SSO) configured app that has been integrated with Azure Active Directory (Azure AD).

Symptoms

You receive error AADSTS75011 when trying to sign into an application that has been setup to use Azure AD for identity management using SAML-based SSO.

Cause

The RequestedAuthnContext is in the SAML request. This means the app is expecting the AuthnContext specified by the AuthnContextClassRef. However, the user has already authenticated prior to access the application and the AuthnContext (authentication method) used for that previous authentication is different from the one being requested. For example, a federated user access to MyApps and WIA occurred. The AuthnContextClassRef will be urn:federation:authentication:windows. AAD won’t perform a fresh authentication request, it will use the authentication context that was passed-through it by the IdP (ADFS or any other federation service in this case). Therefore, there will be a mismatch if the app requests other than urn:federation:authentication:windows. Another scenario is when MultiFactor was used: 'X509, MultiFactor.

Resolution

RequestedAuthnContext is an optional value. Then, if possible, ask the application if it could be removed.

Another option is to make sure the RequestedAuthnContext will be honored. This will be done by requesting a fresh authentication. By doing this, when the SAML request is processed, a fresh authentication will be done and the AuthnContext will be honored. To request a Fresh Authentication the SAML request most contain the value forceAuthn="true".

More Information

For a full list of Active Directory Authentication and authorization error codes see Azure AD Authentication and authorization error codes