How to Resolve LSA Module Blocked Error on Windows 11

The “This module is blocked from loading into the Local Security Authority” error in Windows 11’s Program Compatibility Assistant, often involving mdnsNSP.dll from Apple’s Bonjour service, arises due to enhanced LSA (Local Security Authority) protection in Windows 11 version 24H2 and later. This protection prevents untrusted modules from accessing sensitive authentication data. This guide provides several methods to resolve this error, prioritizing security best practices.

Method 1: Uninstall Bonjour and Related Apple Software

The most straightforward solution is to uninstall Bonjour and potentially other Apple software that might be causing the conflict.

Step 1: Access Installed Apps: Open Windows Settings (Win+I), go to Apps > Installed apps.

Step 2: Uninstall Bonjour: Search for “Bonjour” and uninstall it.

Step 3: Uninstall Other Apple Software (Optional): Uninstall iTunes or other Apple software, as some versions automatically reinstall Bonjour. Restart your computer after uninstalling.

Step 4: Reinstall iTunes (If Needed): If you require iTunes, install the latest version from the Microsoft Store for better compatibility with Windows 11 security features.

Method 2: Disable Bonjour Service Without Uninstallation

Disabling the Bonjour service prevents it from loading into the LSA without completely removing it from your system.

Step 1: Access Services: Open the Run dialog (Win+R), type services.msc, and press Enter.

Step 2: Locate Bonjour Service: Find “Bonjour Service” or “mDNSResponder.”

Step 3: Disable the Service: Right-click the service, select “Properties,” set “Startup type” to “Disabled,” click “Stop” if running, and click “OK.”

Step 4: Restart Your PC: Restart your computer to apply the changes.

Method 3: Remove Bonjour DLL from Network Provider List (Advanced)

This advanced method removes references to mdnsNSP.dll from the network provider list in the Windows Registry. Proceed with caution and create a registry backup before making any changes.

Step 1: Access Registry Editor: Open regedit.exe as an administrator.

Step 2: Navigate to Registry Key: Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\NameSpace_Catalog5.

Step 3: Delete mdnsNSP.dll Entries: Under Catalog_Entries, delete any entries referencing mdnsNSP.dll.

Step 4: Restart Your PC: Restart your computer after making these changes.

Method 4: System File Checker and DISM (For General DLL Errors)

This method addresses potential system file corruption that might contribute to DLL loading issues.

Step 1: Open Command Prompt as Administrator: Open Command Prompt as administrator.

Step 2: Run System File Checker: Run sfc /scannow. This scans for and repairs corrupted system files.

Step 3: Run DISM (If Necessary): If sfc /scannow doesn’t resolve the issue, run DISM /Online /Cleanup-Image /RestoreHealth. This checks for and repairs deeper system image corruption.

Understanding the Root Cause:

Windows 11’s LSA protection blocks DLLs that lack proper digital signatures or don’t meet Microsoft’s security requirements. Bonjour’s mdnsNSP.dll, and similar DLLs from other third-party software, are frequently flagged because they haven’t been updated to comply with the latest security standards. Disabling LSA protection is strongly discouraged as it weakens system security.

Alternative Causes:

Other software, like QuickHeal Antivirus or Entrust authentication modules, may also trigger this error. Update or uninstall these programs if they are suspected.

Conclusion: The “module is blocked” error is often resolved by uninstalling or disabling Bonjour. If the problem persists, using the advanced registry method or the system file checkers may be necessary. Always prioritize security best practices and avoid disabling core security features unless absolutely necessary and you fully understand the implications.