TESTforge42/scanner-bypass-npz-int-desync

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

import numpy as np
z = np.load("model.npz", allow_pickle=True); z[z.files[0]]   # fires the benign marker

picklescan -p model.npz   # exit 0
modelscan -p model.npz     # no issue