| Package | Affected versions | Patched versions |
|---|---|---|
| fugue | ≤ 0.9.2 | |
| fugue | ≤ 0.9.1 |
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.
_decode() function in fugue/rpc/flask.py directly uses cloudpickle.loads() to deserialize data without any sanitization.
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:
In this example, attacker modifies _encode to let the victim execute command “ls -l”
Fugue gives a demo video and the PoC in the attachment, along with modified flask.py. When users reproduce this issue, in the server side (as an victim), users can run python rpc_server.py. In the client side (as an attacker), users can first replace fugue/rpc/flask.py in pip site-packages with provided flask.py in the attachment and then run rpc_client.py.
Remote code execution in the victim's machine. Once the victim starts the RPCServer with network binding (especially 0.0.0.0), an attacker on the network can gain arbitrary code execution by connecting to the RPCServer and sending crafted pickle payloads. This vulnerability allows for:
Replace unsafe deserialization: Replace pickle.loads() with safer alternatives such as:
Unpickler with a restricted method that only allows whitelisted classesRunning one of these products? Scan your site to see whether it exposes a vulnerable version.
Scan my site freefind_class()Network security:
127.0.0.1) instead of 0.0.0.0Security warnings: When starting the service on public interfaces, display clear security warnings to inform users about the risks.