CVE-2026-84811

AgentVerus scanner bypass via malicious __pycache__ bytecode files.

• CVSS 7.1
• 693
• Input Validation and Sanitization
• Remote

agentverus-scanner fails to analyze compiled Python bytecode files in companion code directories, allowing attackers to bypass security scanning by shipping malicious __pycache__ entries alongside benign source files. Attackers can execute arbitrary Python bytecode on import while the scanner reports a CERTIFIED verdict with high trust scores in both static and semantic analysis modes.

CVE

CVE-2026-84811

CWE

693

CVSS base score

7.1

Published

2026-09-02

OWASP

A08 Software and Data Integrity Failures

Orthogonal defect classification

Checking

Code defect classification

Missing Check

Category

Input Validation and Sanitization

Subcategory

Insecure Parsing or Deserialization

Accessibility scope

Remote

Impact

Arbitrary Code Execution

Affected component

Python

import importlib.util
import os

def load_plugin(plugin_dir: str):
    """
    Load the first Python module found in the given directory,
    trusting compiled bytecode files in __pycache__.
    """
    # VULNERABLE: trusts .pyc files in __pycache__ without validation
    for root, _, files in os.walk(plugin_dir):
        for name in files:
            if name.endswith('.pyc'):
                pyc_path = os.path.join(root, name)
                spec = importlib.util.spec_from_file_location("plugin", pyc_path)
                module = importlib.util.module_from_spec(spec)
                spec.loader.exec_module(module)  # executes unvalidated bytecode
                return module
    raise FileNotFoundError("No plugin found")

import importlib.util
import os

def load_plugin(plugin_dir: str):
    """
    Load the first Python module found in the given directory,
    ignoring compiled bytecode files in __pycache__.
    """
    # FIX: ignore .pyc files and only load .py source to prevent unvalidated bytecode execution
    for root, _, files in os.walk(plugin_dir):
        for name in files:
            if name.endswith('.py') and not name.startswith('__init__'):
                src_path = os.path.join(root, name)
                spec = importlib.util.spec_from_file_location("plugin", src_path)
                module = importlib.util.module_from_spec(spec)
                spec.loader.exec_module(module)
                return module
    raise FileNotFoundError("No plugin found")

__VAITP_MODEL_REFUSED__

@misc{vaitp:cve202684811,
  title        = {{AgentVerus scanner bypass via malicious __pycache__ bytecode files.}},
  author       = {Bogaerts, Fr\'ed\'eric and Ivaki, Naghmeh and Fonseca, Jos\'e},
  year         = {2026},
  note         = {VAITP Python Vulnerability Dataset, entry CVE-2026-84811},
  howpublished = {\url{https://netpack.pt/vaitp/vulnerability/CVE-2026-84811/}}
}