This indicates an attack attempt to exploit a Insecure Deserialization Vulnerability in FasterXML jackson-databind.
The vulnerability is due to an input validation error when parsing a crafted HTTP request. A remote attacker could exploit this to execute arbitrary code within the context of target application, via a maliciously crafted JSON input.
FasterXML jackson-databind 2.x before 126.96.36.199
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor