CVE-2025-62703: 
Python vulnerability analysis and mitigation

A remote code execution vulnerability (CVE-2025-62703) was discovered in the Fugue framework's RPC server implementation, affecting versions <=0.9.1. The vulnerability exists in the _decode() function within fugue/rpc/flask.py, which uses cloudpickle.loads() for data deserialization without proper sanitization. This security flaw was discovered and reported by Chenpinji, with the issue being addressed in version 0.9.1 (GitHub Advisory).

The vulnerability stems from unsafe deserialization practices in the FlaskRPCServer implementation. The _decode() function directly uses cloudpickle.loads() to deserialize data without any sanitization mechanisms. The vulnerability has been assigned a CVSS v3.1 score of 8.8 (High), with the vector string CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. The vulnerability is classified as CWE-502 (Deserialization of Untrusted Data) (GitHub Advisory).

The vulnerability enables remote code execution on the victim's machine when the RPCServer is bound to open network interfaces. Successful exploitation can lead to complete system compromise, data exfiltration, lateral movement within the network, denial of service attacks, and installation of persistent backdoors (GitHub Advisory).

Several mitigation strategies have been implemented: 1) Upgrade to version 0.9.1 or later, 2) Replace pickle.loads() with safer alternatives such as JSON serialization, Protocol Buffers, or MessagePack, 3) If pickle must be used, implement a custom Unpickler with a restricted find_class() method, 4) Bind to localhost (127.0.0.1) instead of 0.0.0.0 for internal services, and 5) Implement proper authentication and authorization mechanisms. Security warnings have been added to alert users when starting the service on public interfaces (GitHub Commit, GitHub Advisory).