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RPC_NT_UNSUPPORTED_AUTHN_LEVEL
Unsupported RPC authentication level
RPC_NT_UNSUPPORTED_AUTHN_LEVEL belongs to the Windows RPC runtime NTSTATUS facility. MS-RPCE extends the DCE/RPC model: generated stubs marshal parameters, the runtime binds to an endpoint and protocol sequence, and security or transport failures can be returned as RPC facility status values.
RPC authentication levels describe how much protection is applied to the call, from connection-level checks through packet integrity and privacy. This status means the requested level cannot be used in the current configuration.
Check both sides. The client may request a level the server does not accept, or a server policy may require a level the client binding did not negotiate. DCOM/RPC hardening changes can make old clients fail here.
What to check
- Log the requested and negotiated authentication level, not just the package name.
- Check whether the protocol sequence supports the requested level.
- For enterprise failures, compare affected and unaffected machines for RPC security policy and Windows update level.
References
- Microsoft RPC: client impersonation
- Microsoft RPC: authentication-level constants
- MS-RPCE: security context handle
- Microsoft Open Specifications: MS-RPCE overview
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