Home Assistant Command-line Interface: Handling of user-supplied Jinja2 templates

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.6 · CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:N

EPSS

• CVE-2026-40602: 0.10% estimated exploitation activity in the next 30 days; percentile 0.99 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Up to 1.0.0 of home-assitant-cli (or hass-cli for short) an unrestricted environment was used to handle Jninja2 templates instead of a sandboxed one. The user-supplied input within Jinja2 templates was rendered locally with no restrictions. This gave users access to Python's internals and extended the scope of templating beyond the intended usage. E. g., it was possible to render a template with hass-cli template bad-template.j2 --local that contained entries like or other malicious Jinja2 expressions. This can lead to arbitrary code execution on the local machine. In a two step process an adversary could trick/convince an user to download third-party templates which contain harmful code (e. g., perform data manipulation or establish a remote shell) then to render those templates unchecked/reviewed/verified with --local. The issue only affect the local machine and not a remote Home Assistant instance. It also requires user interventions. Patches 1.0.0 uses…

Published by the source

16 Apr 2026, 21:28 UTC

Last modified by the source

13 Jul 2026, 16:42 UTC

Source last checked

26 Oct 2026, 13:40 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-33qf-q99x-wpm8

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-33qf-q99x-wpm8

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# Patch Next advisory brief: CVE-2026-40602

Advisory: Home Assistant Command-line Interface: Handling of user-supplied Jinja2 templates
IDs: CVE-2026-40602, GHSA-33qf-q99x-wpm8
Record: https://patchnext.com/advisories/cve-2026-40602 (revision 2, source checked 26 Oct 2026, 13:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: homeassistant-cli 1.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI homeassistant-cli: affected < 1.0.0; fixed in 1.0.0

## Suggested inspection (read-only)
- `python -m pip show homeassistant-cli`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on homeassistant-cli.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-33qf-q99x-wpm8 (OSV record GHSA-33qf-q99x-wpm8 lists affected ranges: PyPI homeassistant-cli >=0 <1.0.0 (fixed))
- Verified: https://github.com/advisories/GHSA-33qf-q99x-wpm8 (GitHub-reviewed advisory GHSA-33qf-q99x-wpm8 lists affected ranges: PyPI homeassistant-cli >=0 <1.0.0)

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