Security updates have been released for Exchange 2013, Exchange 2016 and Exchange 2019.
The updates fixes the following Remote Code Execution Vulnerabilities;
None of the vulnerabilities are currently publicly disclosed nor exploited. The Exploitability Assessment is rated: Exploitation More Likely.
View: Exchange Blog: Released: April 2021 Exchange Server Security Updates
View: Microsoft Security Response Center (MSRC) Blog: April 2021 Update Tuesday packages now available
View: Description of the security update for Microsoft Exchange Server 2019, 2016, and 2013: April 13, 2021 (KB5001779)