How to Microsoft Security Troubleshoot Windows
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    Introduction

    After upgrading to Windows Server 2025, many administrators encounter the following error when accessing shared folders, NAS devices, scanners, or legacy SMB storage:

    “An extended error has occurred while accessing network storage.”

    This issue commonly affects:

    • Older NAS devices
    • Samba shares
    • Legacy Windows servers
    • Shared folders using guest access
    • Devices without SMB signing support

    The problem is caused by stricter SMB security policies introduced in Windows Server 2025.

    This guide explains multiple methods to fix the issue using:

    • GPEDIT (Group Policy Editor)
    • REGEDIT (Registry Editor)
    • PowerShell commands

    Why This Happens

    Windows Server 2025 enables stronger SMB security by default, including:

    • Mandatory SMB signing
    • Blocking insecure guest logins
    • NTLM hardening
    • Stricter authentication policies

    Older storage devices often do not support these newer security requirements.

    As a result, Windows refuses the connection and displays the network storage error.

    Method 1 — Fix Using Group Policy (GPEDIT)

    This is the easiest and recommended method for most administrators.

    Step 1: Open Local Group Policy Editor

    Press:

    Win + R

    Type:

    gpedit.msc

    and press Enter.

    Step 2: Enable Insecure Guest Logons

    Navigate to:

    Computer Configuration
→ Administrative Templates
→ Network
→ Lanman Workstation

    Find:

    Enable insecure guest logons

    Set it to:

    Enabled
    Enable Insecure Guest Logons

    Step 3: Disable Mandatory SMB Signing

    Navigate to:

    Computer Configuration
→ Windows Settings
→ Security Settings
→ Local Policies
→ Security Options

    Find:

    Microsoft network client:
Digitally sign communications (always)

    Set it to:

    Disabled
    Disable Mandatory SMB Signing

    Step 4: Apply Policies

    Open Command Prompt as Administrator and run:

    gpupdate /force

    Then reboot the server.

    Method 2 — Fix Using Registry Editor (REGEDIT)

    This method directly modifies SMB client settings in the registry.

    Step 1: Open Registry Editor

    Press:

    Win + R

    Type:

    regedit

    and press Enter.

    Step 2: Navigate to the SMB Workstation Parameters

    Go to:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters

    Step 3: Create or Modify the Following DWORD Values

    Disable Required SMB Signing

    Create or modify:

    "RequireSecuritySignature"=dword:00000000

    Enable Insecure Guest Authentication

    Create or modify:

    "AllowInsecureGuestAuth"=dword:00000001

    Complete Registry Example

    Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters]

"RequireSecuritySignature"=dword:00000000
"AllowInsecureGuestAuth"=dword:00000001
    Disable Required SMB Signing

    Step 4: Restart the Server

    Reboot Windows Server 2025 after applying the changes.

    Method 3 — Fix Using PowerShell

    PowerShell is ideal for automation and server deployments.

    Open PowerShell as Administrator.

    Disable SMB Signing Requirement

    Run:

    Set-SmbClientConfiguration -RequireSecuritySignature $false

    Press:

    Y

    to confirm.

    Verify Current SMB Client Configuration

    Run:

    Get-SmbClientConfiguration

    Check the value for:

    RequireSecuritySignature

    It should now display:

    False

    Enable Insecure Guest Logons via PowerShell

    Run:

    Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters" `
-Name AllowInsecureGuestAuth -Value 1 -Type DWord

    Optional: Enable SMB1 Support (Legacy NAS Devices Only)

    Some old NAS devices still require SMB1.

    Enable SMB1:

    Enable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol

    Then reboot.

    Only enable SMB1 if absolutely necessary because it is outdated and less secure.

    Additional Troubleshooting Steps

    Clear Saved Credentials

    Open Credential Manager:

    control /name Microsoft.CredentialManager

    Remove old entries related to the NAS or file server.

    Test SMB Connectivity

    Run:

    Test-NetConnection SERVERNAME -Port 445

    Example:

    Test-NetConnection 192.168.1.20 -Port 445

    If port 445 fails, SMB traffic may be blocked by:

    • Firewall
    • NAS configuration
    • Antivirus
    • Network policy

    Access Using IP Address

    Instead of:

    \\NAS-SERVER\Share

    try:

    \\192.168.1.20\Share

    This helps identify DNS or hostname resolution problems.

    Security Considerations

    The fixes above reduce SMB security to support older devices.

    Recommended long-term solutions:

    • Upgrade NAS firmware
    • Use authenticated SMB shares instead of guest access
    • Disable SMB1 where possible
    • Enable SMB signing on storage devices
    • Restrict network access using VLANs or firewall rules

    Final Thoughts

    The “An extended error has occurred while accessing network storage” issue in Windows Server 2025 is usually caused by SMB signing enforcement and blocked guest authentication.

    In most environments, the following two changes solve the problem immediately:

    1. Disable required SMB signing
    2. Enable insecure guest logons

    These can be configured using:

    • GPEDIT
    • REGEDIT
    • PowerShell

    If you are connecting to older NAS devices or Samba shares, these compatibility settings are often necessary after upgrading to Windows Server 2025.

    How to Fix “An Extended Error Has Occurred While Accessing Network Storage” on Windows Server 2025

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