Affected: fugue-project fugue

Fugue is a unified interface for distributed computing that lets users execute Python, Pandas, and SQL code on Spark, Dask, and Ray with minimal rewrites. In version 0.9.2 and prior, there is a remote code execution vulnerability by pickle deserialization via FlaskRPCServer. The Fugue framework implements an RPC server system for distributed computing operations. In the core functionality of the RPC server implementation, I found that the _decode() function in fugue/rpc/flask.py directly uses cloudpickle.loads() to deserialize data without any sanitization. This creates a remote code execution vulnerability when malicious pickle data is processed by the RPC server. The vulnerability exists in the RPC communication mechanism where the client can send arbitrary serialized Python objects that will be deserialized on the server side, allowing attackers to execute arbitrary code on the victim's machine. This issue has been patched via commit 6f25326.

Affected: PyPI: fugue

### Summary The Fugue framework implements an RPC server system for distributed computing operations. In the core functionality of the RPC server implementation, I found that the _decode() function in fugue/rpc/flask.py directly uses cloudpickle.loads() to deserialize data without any sanitization. This creates a remote code execution vulnerability when malicious pickle data is processed by the RPC server.The vulnerability exists in the RPC communication mechanism where the client can send arbitrary serialized Python objects that will be deserialized on the server side, allowing attackers to execute arbitrary code on the victim's machine.

### Details _decode() function in fugue/rpc/flask.py directly uses cloudpickle.loads() to deserialize data without any sanitization.

### PoC * Step1: The victim user starts an RPC server binding to open network using the Fugue framework. Here, I use the official RPC server code to initialize the server.

* Step2: The attacker modifies the _encode() function in fugue/rpc/flask.py to inject malicious pickle data:

<img width="740" height="260" alt="image" src="https://github.com/user-attachments/assets/6064516b-e1a6-45fa-a91c-8e276bc4a106" />

In this example, attacker modifies _encode to let the victim execute command “ls -l”

* Step 3: The attacker then uses the RPC client to send the malicious request

Fugue gives a demo video and the PoC in the attachment, along with modified flask.py. When users reproduce this issue, in the server sid…