Deserialization of untrusted data in python in pyfory versions 0.12.0 through 0.12.2 allows arbitrary code execution. An application is vulnerable if it reads pyfory serialized data from untrusted sources. An attacker can craft a data stream that selects pickle-fallback serializer during deserialization, leading to the execution of `pickle.loads`, which is vulnerable to remote code execution. Users are recommended to upgrade to version 0.12.3 or later, which has removed pickle fallback serializer and thus fixes this issue.