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SEC_E_CROSSREALM_DELEGATION_FAILURE
SEC_E_CROSSREALM_DELEGATION_FAILURE identifies a failure in constrained delegation across realm boundaries. The service attempted S4U delegation to a target outside the realm allowed by its current constrained-delegation configuration. Diagnose constrained delegation across realm boundaries at the first component that returned the value, not the last user-interface layer that displayed it; later cleanup and fallback attempts can produce different secondary errors.
Locate the first failing boundary
Service-for-User is a Kerberos extension evaluated by the KDC, not a local password check in a constrained delegation across realm boundaries investigation. Record whether the request is S4U2self or S4U2proxy, the service account and realm, target SPN, ticket flags, contacted domain controller, and the delegation configuration visible to that controller.
Useful observations, not generic logs
- S4U stage, service principal, user principal, target SPN, source and target realms
Log the client realm, service realm, target realm, source service SPN, and target SPN.
In the path, pINs the result to a specific handshake or KDC decision. - KDC or domain controller identity and its supported protocol behavior
Inspect classic or resource-based constrained delegation configuration on both sides of the trust.
Separates identity proof from delegation or transport policy. - Delegation configuration, ticket flags, and the exact failure returned to SSPI
Verify that DNS canonicalization and SPN aliases are not making an in-realm service appear cross-realm.
Keeps target names, package selection, and context state comparable.
Correlate the failure with state changes
In the path, authentication failures are multi-leg transactions. Align client SSPI calls, DNS and target-name resolution, policy refresh, domain-controller or KDC events, ticket acquisition, server acceptance, and any proxy or TLS transition. A single application timestamp is not enough to tell whether the decision was local policy, peer identity, context state, or KDC behavior.
- Package and target name, requested and returned context attributes, and each SSPI return in order.
- In the path, relevant Group Policy result, SPN or UPN resolution, contacted DC/KDC, and ticket or certificate identities.
- One permitted control target and one deliberately rejected target evaluated with the same client build in a constrained delegation across realm boundaries investigation.
Reproduction without destructive cleanup
Test an in-realm target already allowed for constrained delegation before testing the failing cross-realm or unsupported path. This separates basic service-account configuration from the realm boundary or KDC capability that selected the status.
| Test | Interpretation |
|---|---|
| Same input, known-good path | For constrained delegation across realm boundaries, success moves attention toward the selected provider, policy, device, context, or transaction state. |
| Known-good input, failing path | For constrained delegation across realm boundaries, failure suggests that the environment or selected object is independently unable to perform the operation. |
| Original path after one isolated change | For constrained delegation across realm boundaries, this comparison demonstrates whether the proposed correction addresses the original condition. |
How this differs from similar failures
Ordinary Kerberos cross-realm authentication can work while constrained delegation still fails; the delegated hop has additional authorization rules. Changing application credentials does not add S4U support to a domain controller and does not extend a constrained-delegation allow-list., keep protocol capability and account authorization separate.
For constrained delegation across realm boundaries, also retain the original numeric value; neighboring constants can encode materially different remediation paths even when an application presents all of them as an authentication, certificate, or security failure.
Regression check
The intended KDC must issue the required ticket for the configured target and realm while preserving the expected delegation restrictions in a constrained delegation across realm boundaries investigation. Keep a regression case that uses nonsecret identifiers and expected outcomes, including one negative control that must continue to fail.
Technical references
These sources define the HRESULT and the relevant constrained delegation across realm boundaries interface, protocol, or data format.
- Microsoft Open Specifications: HRESULT values.
- Microsoft Open Specifications: Kerberos S4U.
- Microsoft Open Specifications: S4U2proxy.
- RFC 4120: The Kerberos Network Authentication Service.
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