Microsoft Exchange Exploit Attempt - CVE-2021-42321

Microsoft Exchange has a remote code execution (RCE) vulnerability in the Exchange Web Services (EWS) endpoint, /ews/exchange.asmx. To exploit the vulnerability, the attacker submits a series of consecutive HTTP requests with SOAP messages. SOAP is an XML-based message protocol. First, the attacker sends a SOAP message that results in the exposure of inbox variable values. With these values, the attacker can delete existing user configurations for the inbox. Next, the attacker uploads a new user configuration by sending an HTTP request with a SOAP message that contains a malicious serialized payload. Finally, the attacker sends another SOAP message that causes the Exchange server to read the new user configuration and deserialize the malicious payload, running code on the victim.