What is SMB-SIGN-MISMATCH?
SMB signing mismatch – network share unavailable (SMB-SIGN-MISMATCH) is a medium-severity fault affecting the Windows operating system. Cannot connect to a Windows file share. Error: 'The network path was not found' or 'Access denied' due to SMB signing policy conflict. Common triggers are outdated NAS firmware with SMB1 only and firewall blocking port 445. Follow the steps below to fix it.
Common Causes
- Server requires SMB signing but client has it disabled
- Outdated NAS firmware with SMB1 only
- Firewall blocking port 445
Step-by-Step Fix Guide
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1
Enable SMB signing on client: Set-SmbClientConfiguration -RequireSecuritySignature $true
If earlier steps didn't help, "Enable SMB signing on client: Set-SmbClientConfiguration -RequireSecuritySignature $true" directly addresses server requires SMB signing but client has it disabled.
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2
Update NAS firmware to support SMB2/SMB3
If earlier steps didn't help, "Update NAS firmware to support SMB2/SMB3" directly addresses outdated NAS firmware with SMB1 only.
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3
Allow TCP port 445 in Windows Firewall
This step, "Allow TCP port 445 in Windows Firewall", specifically rules out firewall blocking port 445.
Commands & Diagnostics
Get-SmbClientConfiguration
Get-SmbServerConfiguration
Test-NetConnection -ComputerName SERVER -Port 445
Frequently Asked Questions
Server requires SMB signing but client has it disabled accounts for the majority of SMB-SIGN-MISMATCH reports; outdated NAS firmware with SMB1 only and firewall blocking port 445 come up less often but are documented.
The fastest fix is "Enable SMB signing on client: Set-SmbClientConfiguration -RequireSecuritySignature $true". Only move on to the later steps if SMB-SIGN-MISMATCH keeps coming back.
SMB-SIGN-MISMATCH is a medium-severity issue. It can affect system stability, but the fix steps above typically resolve it without lasting damage.
Usually. SMB-SIGN-MISMATCH is fixable with the steps above; a full Windows reinstall is rarely necessary unless everything else has failed.
Sometimes. Microsoft regularly releases patches that fix known BSOD triggers including SMB-SIGN-MISMATCH. Make sure Windows is fully up to date via Settings → Windows Update before attempting more advanced fixes.
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