An issue was discovered in Treasure Data Fluent Bit, where erroneous parsing in `flb pack msgpack to json format` leads to a type confusion bug. This bug interprets whatever is on the stack as msgpack maps and arrays, leading to use-after-free. An attacker can craft a specially crafted file and trick the victim into opening it using the affected software, triggering use-after-free and executing arbitrary code on the target system.