CVE-2026-84202

Unsafe PyYAML loader enables arbitrary code execution via malicious model config.

• CVSS 8.7
• 502
• Input Validation and Sanitization
• Remote

ModelScope uses PyYAML's unsafe yaml.Loader to parse model configuration files, allowing arbitrary code execution through Python object construction tags. Attackers can craft malicious model repositories with poisoned configuration files that execute code when loaded by users.

CVE

CVE-2026-84202

CWE

502

CVSS base score

8.7

Published

2026-09-01

OWASP

A08 Software and Data Integrity Failures

Orthogonal defect classification

Interface

Code defect classification

Missing Check

Category

Input Validation and Sanitization

Subcategory

Insecure Parsing or Deserialization

Accessibility scope

Remote

Impact

Arbitrary Code Execution

Affected component

PyYAML

Fixed by upgrading

Yes

Solution

Upgrade ModelScope to a version that replaces yaml.Loader with yaml.safe_load (e.g., v1.9.0 or later), and ensure all configuration files are parsed with yaml.safe_load to prevent unsafe object construction.

import yaml

def load_model_config(path: str) -> dict:
    """Load a ModelScope model configuration file."""
    with open(path, 'r') as f:
        # VULNERABLE: using unsafe yaml.Loader allows arbitrary object construction
        config = yaml.load(f, Loader=yaml.Loader)
    return config

import yaml

def load_model_config(path: str) -> dict:
    """Load a ModelScope model configuration file."""
    with open(path, 'r') as f:
        # FIX: use safe_loader to prevent object construction
        config = yaml.safe_load(f)
    return config

__VAITP_MODEL_REFUSED__

@misc{vaitp:cve202684202,
  title        = {{Unsafe PyYAML loader enables arbitrary code execution via malicious model config.}},
  author       = {Bogaerts, Fr\'ed\'eric and Ivaki, Naghmeh and Fonseca, Jos\'e},
  year         = {2026},
  note         = {VAITP Python Vulnerability Dataset, entry CVE-2026-84202},
  howpublished = {\url{https://netpack.pt/vaitp/vulnerability/CVE-2026-84202/}}
}