Fix SMB without password is not accessible issue in Windows 10.

How to solve the problem that Windows 10 SMB client can not access SMB server with guest account that has no password?

Error Description

When access SMB server with guest account that has no password:

Error Description from file explorer：

visit \\SMB-name-or-ip (for example \\192.168.1.111) in address bar：

Windows cannot access \\ip Check the spelling of the name. Otherwise, there might be a problem with your network. To try to identify and resolve network problems, click Diagnose.

visit \\ip:port in address bar (port for smb is 445 or 139, but any number give the same error message)：

\\ip:port is not accessible. You might not have permission to use this network resource. Contact the administrator of this server to find out if you have access permissions. The parameter is incorrect.

Error Description from powershell New-SmbMapping -LocalPath 'S:' -RemotePath '\\SMB-name-or-ip\folder'：

New-SmbMapping : You can't access this shared folder because your organization's security policies block unauthenticated guest access. These policies help protect your PC from unsafe or malicious devices on the network. At line:1 char:1

+FullyQualifiedErrorId : Windows System Error 1272,New-SmbMapping

Solution

Make sure you do both the "Local Group Policy Editor" step AND the "Registry Editor" step (unless the register key does not exist in the first place).

Local Group Policy Editor

run gpedit -> Computer configuration\administrative templates\network\Lanman Workstation\"Enable insecure guest logons" -> set "Enable"

Registry Editor

run regedit -> HKLM\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters -> if "AllowInsecureGuestAuth" exist set it to "1"

Restart computer

done!

You can't access this shared folder because your organization's security policies block unauthenticated guest access. - Microsoft Q&AMicrosoftLearn

Thoughts

The error description provided by Windows 10 file explorer is useless, irrelevant and misleading. The key lies in the settings of the SMB client, not the sever. The setting is in group policy template but is overridden by a registry key hidden in the registry (which is not updated when group policy is changed).