The Home Assistant Command‑line interface (hass‑cli) previously used an unrestricted Jinja2 environment to render user‑supplied templates, allowing full access to Python’s internals. As a result, an attacker could construct a malicious template that executes arbitrary Python code locally. This vulnerability is a classic example of improper restriction of operations (CWE‑1336) and improper code generation control (CWE‑94), and it permits local code execution beyond the intended templating functionality.

The bug affects the Home Assistant Ecosystem’s home‑assistant‑cli product, specifically all releases up to and including 0.x versions; the vulnerability was fixed in version 1.0.0 and later.

The CVSS score of 5.6 indicates medium severity, and the vulnerability is not listed in the CISA KEV catalog. Exploitation requires local access to the hass‑cli utility or the ability to supply a template to the tool, meaning the threat is confined to users with sufficient privilege on the host machine. If those conditions are met, an attacker can run arbitrary code on the system, potentially leading to full compromise of the host.