This vulnerability allows remote attackers to execute arbitrary code on affected installations of Microsoft Exchange Server. Although authentication is required to exploit this vulnerability, the existing authentication mechanism can be bypassed. The specific flaw exists within the OAB service. The issue results from the lack of proper validation of user-supplied data, which can allow arbitrary files write to OAB folders. An attacker can leverage this vulnerability to execute arbitrary code in the context of SYSTEM.
Security Updates for Exchange (May 2021)
Description of the security update for Microsoft Exchange Server 2019, 2016, and 2013: May 11, 2021 (KB5003435)
Wormable Windows Bug Opens Door to DoS, RCE
Patch Tuesday - May 2021