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| ERROR_LOCAL_USER_SESSION_KEY | ERROR_UNKNOWN_REVISION |
ERROR_NULL_LM_PASSWORD
The password has no usable LAN Manager representation
This result belongs to legacy password compatibility, not to ordinary password verification. Older Windows authentication paths could maintain both an NT password hash and a LAN Manager hash. An LM representation can be unavailable when the password cannot be represented by the legacy algorithm or when LM-hash storage has been disabled. In that situation a caller expecting the LM form receives a null LM password value even though the account can still have a valid NT password representation.
Treat the status as evidence that an old password-management or authentication path is asking for obsolete material. Identify the exact client and SAMR password-change method before changing policy. Modern NTLM and Kerberos scenarios do not require an LM hash merely because an account password exists. Enabling LM-hash storage to satisfy one old component weakens password protection and should not be used as a generic repair.
What to inspect
- Identify whether the client is using an LM/OEM password-change path or a modern Unicode path.
- Check the NoLMHash policy and the age of the client or management library.
- Do not interpret a null LM representation as proof that the user supplied the wrong current password.
References
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