Symptoms
Assume that you use Microsoft SQL Server 2017 Express LocalDB (SqlLocalDB). When you create a database, you receive an error message that resembles the following:
Msg 5123, Level 16, State 1, Line 1
CREATE FILE encountered operating system error 5(Access is denied.) while attempting to open or create the physical file 'C:\Users\username_dbfilename.mdf'. Msg 1802, Level 16, State 4, Line 1 CREATE DATABASE failed. Some file names listed could not be created. Check related errors.Resolution
The fix for this problem is included in Cumulative Update 6 for SQL Server 2017.
About SQL Server 2017 builds
Each new build for SQL Server 2017 contains all the hotfixes and security fixes that were in the previous build. We recommend that you install the latest build for SQL Server 2017.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
References
Learn about the standard terminology Microsoft uses to describe software updates.