KB4578012 - FIX: Unable to use Filestream on Windows Server 2012 or Windows 8 after applying SQL Server 2017 CU21

Applies to: SQL Server 2017 Developer on WindowsSQL Server 2017 Enterprise Core on WindowsSQL Server 2017 Enterprise on Windows

Symptoms


After you apply Cumulative Update 21 (CU21) of SQL Server 2017 on Windows Server 2012 or Windows 8, the Filestream and FileTable features may not work properly. 

You may see the following message in the server ERRORLOG:

FILESTREAM: failed to connect to kernel driver RsFx0504. <{1038F43D-3391-45F7-B1B3-BADF26459429}>Failed to initialize CFsaShareFilter: Error 0x80070002 (-2147024894)

You may see the following message in the Windows system event log:

The RsFx0504 Driver service failed to start due to the following error: Windows cannot verify the digital signature for this file. A recent hardware or software change might have installed a file that is signed incorrectly or damaged, or that might be malicious software from an unknown source.

Additionally, you may experience failures when you try to install the CU or enable the Filestream feature after the CU is installed. 

Status


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. 

Resolution


This issue is fixed in the following cumulative update for SQL Server:
About cumulative updates for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:

Workaround


To work around this issue, you can uninstall CU21. 

References


Learn about the terminology that Microsoft uses to describe software updates.