Since Windows Update kb4340556: VBA COM .NET Automation error on CreateObject()

Question

Since the update Windows7 Update KB 4340556 of the Jul 10, 2018 we get the following error message:

"Automation Error" : The system cannot find the file specified" from the Access VBA CreateObject() call.

 Set ComClass = CreateObject("MyApplication1.InteropStart")

Microsoft identifies this as a security issue.

If we uninstall the update KB4340556, the call will work as before.

Does anyone have the same problem? Or a better solution than the update to uninstall?

Answer 1

We were affected with multiple customers too.

I ruled out invalid strong-name signing of our assemblies, since the .NET Assemblies from the Framework itself were affected by that access-denied error too.

Finally I managed to solve the issue by configuration. Apparently the authenticating identity of the website has now to match the identity of the app-pool. Or IUSR has no longer enough permissions.

Answer 2

Our Interop .Net Assembly had a signature with a strong name. The signing is apparently no longer accepted. Creating a new signature (* .snk file) in Visual Studio causes the CreateObject ComInterop call to work again.

EDIT 26.07.2018

We enabled User Account Control (UAC) on the machines from our customers like Pao'lino described.

Creating a new signature also create a new public key token for the assembly. This causes reference problems.