Microsoft has released security updates for vulnerabilities found in:
Exchange Server 2013
Exchange Server 2016
Exchange Server 2019
All versions (Cumulative Update levels) are impacted. ...
Updated Aug 05, 2021
Version 15.0
Blog Post
LukasSMSFT
Microsoft
Microsoft
Can you clarify if the patches for 2016 CU20 and CU21 are identical or not? They have the exact same KB number but the files seem to be different.
No, there are different update packages for CU20 and CU21. You can check the file hash information section at the bottom of the KB: Description of the security update for Microsoft Exchange Server 2016: July 13, 2021 (KB5004779)
Exchange 2016 + CU20 + July 2021 SU + /PrepareSchema (using June 2021 CU) --> Vulnerabilities addressed
Exchange 2016 + CU21 + July 2021 SU --> Vulnerabilities addressed
Can you also clarify if we have exchange 2016 CU20, then install this security patch (CU20 version).
Then after a while we update to CU21. Will we then have to install this security patch again (CU21 version)
Yes, you must install the latest July 2021 SU on top of CU21 (even if you've installed it for CU20) to address all vulnerabilities.