SAML SSO login fails with error "Invalid binding type detected during processing"

Issue

After updating the SAML SSO module, the Service Provider-initiated login fails, and the user is not logged in. The runtime log reports Invalid binding type detected during processing.

ERROR - SAML_SSO: Error occurred while making request: Invalid binding type detected during processing

Environment

SAML v4.2.4 and newer

Cause

This mismatch occurs when the SAML module's response protocol binding differs from the binding the identity provider (IdP) actually uses. The module is configured to expect Artifact binding for the response, while the IdP (e.g., Microsoft Entra ID) returns the SAML response over HTTP-POST binding.

When the SAML configuration specifies the response protocol binding as ARTIFACT_BINDING but the IdP sends the response using POST_BINDING, the module routes the incoming POST response through the artifact resolver, detects the mismatch, and throws Invalid binding type detected during processing.

Solution/Workaround

Update the SAML configuration so the Response protocol binding matches what the IdP sends. For Microsoft Entra ID (and most IdPs that use HTTP-POST), set it to POST_BINDING:

1. Open the SAML module configuration in the running application (the SSO configuration page) and edit the relevant IdP configuration.

2. Locate the Response protocol binding setting and change it from ARTIFACT_BINDING to POST_BINDING.

3. Save the configuration and retry the SSO login.

Additional information

• Mendix documentation:
  • SAML
  • SAML module (Mendix Marketplace)