This indicates an attack attempt to exploit an Insecure Deserialization Vulnerability in Apache Software Foundation Log4j.
The vulnerability is due to deserialization of untrusted data while having a vulnerable version of the JRE library. A remote, unauthenticated attacker can exploit this vulnerability by sending a specially crafted serialized object. Successful exploitation can result in arbitrary code execution with privileges of the user running the application.
Apache Software Foundation Log4j 1.2 to 1.2.17
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.