Dennisdsmolinski Yes. You can install CU14 in the organization with versions that are supported for Exchange 2019 coexistence. 🙂
Also - no, there is no security update for Exchange Server 2016 released today. Only the CU for E2019. For Exchange 2016, you should still enable EP to address the CVE.
Prasad3435 Not today. Exchange 2016 does not get CUs anymore. We do not have SU released for Exchange 2016 today. Might in the future, though, as long as it is a supported product. Note that an update is not needed for Exchange 2016 to address the CVE, Enabling EP is the way.
Marvin_Dickhaus That is correct. As of today, CU12 is considered "out of support". In the future, CU12 will not be getting any more SUs.