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ERROR_CS_ENCRYPTION_INVALID_SERVER_RESPONSE
The server entered Client-Side Encryption mode but returned unusable data
In this error family, Client-Side Encryption is the SMB/EFS workflow for remote encrypted files, not SMB 3 transport encryption. The client expected a response consistent with an encrypted-file open or control operation, but the returned structure or state could not be accepted.
Capture the complete SMB create and FSCTL exchange before retrying. An incompatible server implementation, malformed response, stale handle, or damaged EFS metadata can all produce a protocol-state mismatch. Changing NTFS ACLs does not correct an invalid protocol response.
What to inspect
- Server implementation, SMB dialect, create disposition, and the exact failing request.
- Response structure lengths and fields, including the file identifier used by later FSCTLs.
- Reconnect, retry, and durable-handle paths that may reuse stale CSE state.
- Behavior against a supported Windows file server with the same file and client.
References
- Microsoft: System error codes 6000-8199
- Microsoft Open Specifications: Win32 error codes
- Microsoft Open Specifications: NTSTATUS values
- Microsoft Open Specifications: Existing encrypted-file open algorithm
- Linux ksmbd: SMB status definitions
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