Home Assistant Command-line Interface: Behandlung von benutzerdefinierten Jinja2-Vorlagen

The unrestricted Jinja2 template rendering allows attackers to bypass intended security restrictions within the hass-cli tool. By crafting malicious Jinja2 templates, an attacker can gain access to Python's internals and execute arbitrary code on the system where hass-cli is running. This could lead to complete system compromise, including data theft, modification, or denial of service. The ability to import arbitrary modules and execute code significantly expands the potential attack surface, enabling attackers to perform actions beyond the intended scope of the tool. The vulnerability's impact is amplified if the hass-cli tool is run with elevated privileges.

Home Assistant users who are running versions of hass-cli prior to 1.0.0, particularly those who allow users to provide custom templates or scripts to the CLI tool, are at significant risk. Shared hosting environments where multiple users have access to the hass-cli tool are also vulnerable.

• linux / server:

ps aux | grep 'hass-cli template' | grep -i 'environ.__globals__'

• python / supply-chain:

import os
import subprocess

# Example of a malicious template execution (DO NOT RUN)
subprocess.run(['echo', 'Malicious code executed!'], shell=True)

• generic web: Inspect Home Assistant logs for any errors or unusual activity related to template rendering or Python execution.

1. 2026-04-21Disclosure

   disclosure

1. Reserviert2026-04-14
2. Veröffentlicht2026-04-21
3. EPSS aktualisiert2026-04-29

The primary mitigation for CVE-2026-40602 is to upgrade to version 1.0.0 of the Home Assistant Command-line interface. This version addresses the unrestricted Jinja2 template rendering issue by implementing a sandboxed environment. If upgrading is not immediately feasible, consider restricting access to the hass-cli tool and carefully reviewing any user-supplied templates. While a direct WAF rule is unlikely to be effective due to the nature of the vulnerability, monitoring for suspicious Python code execution patterns within the system's logs can provide an early warning. After upgrading, confirm the fix by attempting to render a malicious Jinja2 template and verifying that it is properly sandboxed and does not execute arbitrary code.