Bug Alert: Can't Access Shared Folders via UNC Alias

UNC aliases are a great way to set up development environments for Access applications that rely on UNC paths. It's too bad Microsoft broke them.

Bug Alert: Can't Access Shared Folders via UNC Alias

I recently wrote an article about how to create a UNC alias for a local folder.  This technique allows you to set up a development environment for Access applications that link to back-end files via UNC paths.  Unfortunately, a recent Windows update broke this feature.  Here are the details.

How it Worked Before the Security Update

My computer name is gbm18.  Here are the shared folders on my computer:

After going through the steps outlined in my UNC Alias article, I had a UNC alias of ams2 for my computer.  As you can see, I have access to the same set of shared folders via this UNC alias:

Note that both of the above screenshots were taken from the gbm18 device.

How it Looks After the Security Update

After the security update, the gbm18 shared folders remained the same:

However, the shared folders were no longer visible via the ams2 alias:

Note that the UNC alias itself still worked.  It simply lost its access to the shared folders.

Identifying the Culprit

The update that broke this feature is KB5009543:

I uninstalled the update via the Control Panel and then restarted my computer.  After the reboot finished, the shared folders were accessible via ams2 once more:

I will be reporting this bug to Microsoft.  Hopefully, this is something that can be addressed and is not itself a vulnerability.  The ability to set up development environments using this technique is an important one and I would be incredibly sad to lose access to it so soon after I learned about it. 😢

UPDATE [2022-02-06]: Official Fix Released

As Ryan W wrote in the comments below, Microsoft released several out-of-band updates to address the bug.  

The specific update you need to install is closely tied to your Windows version.  One of the links below should work for most of my readers.  Refer to the link above for other Windows O/S versions.

Thanks, Ryan W!

External references

January 11, 2022—KB5009543 (OS Builds 19042.1466, 19043.1466, and 19044.1466)

Referenced articles

UNC Alias for a Local Folder
The subst command lets us mimic mapped network drives. But what if your backend tables are linked using UNC paths? Don’t worry. We can handle those, too!

All original code samples by Mike Wolfe are licensed under CC BY 4.0