Earlier this week, Microsoft rolled out a handful of updates to all supported versions of Windows as part of its Patch Tuesday tradition. The updates came with a few known issues, but it seems that at least managed to slip past the company's testing before going public.
According to a number of reports on Reddit and Microsoft's TechNet forums, KB4480970, this month's rollup of security updates to Windows 7 and Windows Server 2008 R2 with Service Pack 1, is causing SMBv2 shares to be inaccessible once it is installed on the host. Customers using Windows Server 2008 Service Pack 2 are seeing similar problems with the respective monthly rollup, KB4480968. Additionally, Remote Desktop access may also fail for users whose accounts reside in the "Administrators" group on target machines, aside from the administrator account itself, after the update according to some reports.
Right now, the easier solution might be simply uninstalling the latest update, which seems to have fixed the issue for those who have reported it. If you feel comfortable editing the registry on your computer, a workaround has been posted on German forums at administrator.de. Of course, editing the registry does carry certain risks, so make sure you have a backup before you proceed. To fix the problems, enter the following command in a Command Prompt window with administrator rights on the host computer:
reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\system /v LocalAccountTokenFilterPolicy /t REG_DWORD /d 1 /f
As of yet, Microsoft doesn't seem to have acknowledged the problem, and it hasn't been added to the list of known issues. Hopefully, a fix will be issued sooner rather than later.
Have you suffered from any problems after the latest update? Let us know in the comments!