On Tuesday, January 8, 2019, Microsoft released monthly patches for January. These included security updates and monthly rollups. Reports quickly surfaced that KB4480970 and KB4480960 were causing issues with SMBv2 shares. Users with local administrator permissions were no longer able to access their network folders and mapped network drives. Standard local users and domain users were not affected.
By Wednesday afternoon, Microsoft had acknowledged issues with KB4480970 and KB4480960. The issue surfaces when a user, who is a member of the local administrator group, tries to access a shared folder on another computer. Microsoft has posted a workaround of using a standard (non-administrative) user or a domain user account. It does appear that domain administrator accounts are not having this problem, only local administrators.
For now, the fix is to uninstall the update on all affected computers. After a reboot, the ability to browse shared folders is restored. Here’s how to uninstall the update:
- Open Windows Control Panel and navigate to Program and Features > Installed Updates page which lists all recently installed updates on the system.
- You can browse the listing manually and find the update KB4480970 or KB44809760.
- Once located, right-click it and select uninstall from the context menu.
- Windows will uninstall the update.
- Reboot PC and you’ll be able to access the network once again.
For more information, Günter Born has written an in-depth analysis that includes a workaround involving a registry change.
Have you or your company been affected by KB4480970 or KB4480960? Please let us know in the comments.