ERROR_NULL_LM_PASSWORD - 1304 (0x518)
The password is too complex to be converted to a LAN Manager password. The LAN Manager password returned is a NULL string.
Updated: Feb 21, 2026
Technical Meaning
The ERROR_NULL_LM_PASSWORD error (1304, 0x518) indicates that a password provided for authentication purposes is too complex to be converted into a LAN Manager (LM) hash. The LM hash returned in this scenario will be an empty string.
Error Details
This error typically occurs during the process of converting a user's password into both NTLM and LM hashes, which are used for different types of authentication mechanisms on Windows systems. When a password is too complex or contains characters that cannot be represented in the 7-bit ASCII format required by the LM hash algorithm, it fails to generate a valid LM hash.
Usage Context
This error can arise when attempting to authenticate users through various Windows APIs and services that rely on both NTLM and LM hashes. It is particularly relevant in scenarios where legacy systems or protocols require LM hashes for compatibility reasons.
Developer Interpretation
Developers should be aware that this error does not necessarily indicate a failure of the authentication process itself, but rather an issue with the password format. The system will still attempt to authenticate using NTLM if an LM hash cannot be generated. However, applications and services that specifically require both NTLM and LM hashes may fail.
Related Errors
ERROR_PASSWORD_MUST_CHANGE(1305)ERROR_PASSWORD_RESTRICTION(1326)
FAQ
Q: What causes the ERROR_NULL_LM_PASSWORD?
A: The error occurs when a password contains characters that cannot be represented in the 7-bit ASCII format required by the LM hash algorithm.
Q: Can this error affect user authentication?
A: No, the system will still attempt to authenticate using NTLM. However, applications and services requiring both NTLM and LM hashes may fail.
Summary
The ERROR_NULL_LM_PASSWORD is a specific technical error that occurs when a password cannot be converted into an LM hash due to its complexity or character set. Developers should handle this scenario by ensuring compatibility with systems that require both NTLM and LM hashes, while still allowing for successful authentication through NTLM alone.