KB4480970 blocks SMB shares. The FIX.

The patch KB4480970is a Monthly Rollup update for Windows 7. It addresses a number of issues in PowerShell, fixes a vulnerability known as Speculative Store Bypass (CVE-2018-3639) for AMD-based computers, and includes Security updates to Windows Kernel, Windows Storage and Filesystems, Windows Wireless Networking, and the Microsoft JET Database Engine.

Unfortunately, the update causes issues with networking. After installing KB4480970 on a Windows 7 PC that has shared folders (using SMB protocol), the shares can not be connected to anymore!!!

Here is the Workaround (Fix):

 Option #1. Uninstall the KB4480970 update

  1. Open a new command prompt as Administrator.
  2. Type the following command: wusa /uninstall /kb:4480970
  3. The update is now uninstalled.

Wusa.exe is the Windows Update Standalone Installer. The Wusa.exe file is in the %windir%\System32 folder. The Windows Update Standalone Installer uses the Windows Update Agent API to install and remove update packages.

Option #2. Apply a Registry fix

If you cannot uninstall the update package, or you need to keep it installed due to security fixes it provides, you can apply the following Registry tweak.

Open Command Prompt with administrator privileges, and run the following command:

  • reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\system /v LocalAccountTokenFilterPolicy /t REG_DWORD /d 1 /f
  • Reboot your PC.

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