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CO_E_FAILEDTOIMPERSONATE
DCOM server could not impersonate the client
CO_E_FAILEDTOIMPERSONATE is HRESULT 2147549475 (0x80010123) from winerror.h. The documented description is “Unable to impersonate DCOM client.” The relevant context is the COM IAccessControl, DCOM client identity, trustee translation, token inspection, security descriptor, ACL, or serialization workflow.
What to verify
Verify that the call is authenticated, requested impersonation level permits impersonation, and the server thread still has an active call context. That boundary prevents this result from being misclassified as corruption, network failure, or a reason for an unsafe automatic retry.
Where it is encountered
- This result can be returned during IAccessControl initialization, access checks, owner/trustee processing, and serialized ACL persistence.
- This result can be returned during server-side DCOM impersonation, client blanket inspection, token and SID lookup.
- It can be returned during security descriptor construction, DACL canonicalization, file-backed policy storage, or legacy NetAccess migration.
The immediate focus is server-side client impersonation needed to perform access checks or resource operations under caller identity.
Correct handling and recovery
Correct COM security and impersonation levels, perform the operation within the call, or use explicit delegated credentials only through supported policy.
An unchanged retry loop can duplicate effects, deepen reentrancy, or hide an invalid lifetime transition.
Difference from nearby HRESULTs
It is a failed impersonation attempt; RPC_E_UNSECURE_CALL says the call was not secure enough to attempt it.
Developer and administrator guidance
After it, avoid broad permission grants or system-wide resets unless code-specific evidence proves a global configuration problem.
Practical scenario
A DCOM file broker tries to impersonate after queuing work beyond method return. It moves the protected open into the active call or captures an approved token safely.
References
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