kotaemon 0.12.0 Unauthenticated Remote Code Execution via Insecure Deserialization

kotaemon through 0.12.0 contains an insecure deserialization vulnerability in the check_connection endpoint that allows unauthenticated attackers to instantiate arbitrary Python classes by supplying crafted YAML/JSON input with a __type__ field. Attackers can exploit this to override the __type__ field with subprocess.check_output and arbitrary arguments, achieving remote code execution with application process privileges.