---
license: apache-2.0
tags: [security-research, huntr, model-file-security, scanner-bypass, numpy]
---
# picklescan & ModelScan bypass: .npz ZIP-container with an object-dtype member carrying an INT-opcode desync
Benign PoC for the huntr Model File Format program. Payload writes only a nonce marker — no real harm.
## Vulnerability
A NumPy .npz is a ZIP of .npy members. Both scanners RECURSE into the .npz and scan each member (positive control: a plain malicious object-.npy inside the .npz is CAUGHT by BOTH). This PoC's object-dtype member carries the INT-opcode desync prefix "I0x10\n": genops parses base-10 and aborts before the payload, while np.load(..., allow_pickle=True)[member] parses "0x10" base-0 and executes the embedded __reduce__ payload. Distinct ZIP-recursion code path + real npz member-access loader ($1500 non-pickle tier).
## Measured (2026-07-24): picklescan 1.0.5 exit 0; ModelScan 0.8.8 no issue; np.load(...,allow_pickle=True) fires the benign marker.
## Reproduce
```python
import numpy as np
z = np.load("model.npz", allow_pickle=True); z[z.files[0]]   # fires the benign marker
```
```bash
picklescan -p model.npz   # exit 0
modelscan -p model.npz     # no issue
```