Windows & BSOD · medium

How to fixSMB-SIGN-MISMATCH

SMB signing mismatch – network share unavailable

What this error means

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 Common triggers are outdated NAS firmware with SMB1 only and firewall blocking port 445.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.

Before you begin

Save open work and back up important files. Note any recent driver or hardware changes. If Windows cannot start, use the startup guide first.

Work through these checks

0 of 3 complete
01Enable SMB signing on client: Set-SmbClientConfiguration -RequireSecuritySignature $true

Enable SMB signing on client: Set-SmbClientConfiguration -RequireSecuritySignature $true.

Use the instructions for your exact device and operating system. Check the manufacturer’s documentation before changing firmware, hardware, or system settings.

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02Update NAS firmware to support SMB2/SMB3

Update NAS firmware to support SMB2/SMB3.

Use the instructions for your exact device and operating system. Check the manufacturer’s documentation before changing firmware, hardware, or system settings.

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03Allow TCP port 445 in Windows Firewall

Allow TCP port 445 in Windows Firewall.

Use the instructions for your exact device and operating system. Check the manufacturer’s documentation before changing firmware, hardware, or system settings.

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Possible causes

  • Server requires SMB signing but client has it disabled
  • Outdated NAS firmware with SMB1 only
  • Firewall blocking port 445