How to update Windows Defender mpsigstub.exe?

I'm trying to put together a script which will update Windows 7 with the latest Windows Defender Antivirus definitions. Microsoft continues to provide updates on their website, being most recently updated July 2021.

Offline definitions can be downloaded and installed offline. This will successfully update the definitions file. However, it is not updating mpsigstub.exe, despite the updated file being contained in the definition update mpas-fe.exe.

Windows Update will continue to report that the latest definitions are not yet installed but will reduce the file size to only a few hundred kilobytes. Downloading this update will correctly update only mpsigstub.exe as expected.

Both mpsigstub.exe and the definitions can be updated automatically while online by running the following command:

cd %ProgramFiles%\Windows Defender
MpCmdRun.exe -removedefinitions -dynamicsignatures
MpCmdRun.exe -SignatureUpdate

The issue I'm experiencing, as mentioned earlier, is that running the offline definitions update mpas-fe.exe will not update mpas-fe.exe and leaves the system vulnerable to CVE-2019-1161.

There is a thread on Microsoft's TechNet forum where a user says:

I found a way to update it. If I launch manually the windows defender it will update automatically the MpSigStub.exe.

I have tried running Windows Defender, stopping/starting the service, and rebooting, but nothing I have tried will update this file.

How can I update mpsigstub.exe offline as desired?

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