CVE-2026-53456: Blueprint Studio Information Disclosure

CVE-2026-53456 Overview

CVE-2026-53456 is a credential exposure vulnerability in Blueprint Studio, a VS Code-like file editor for Home Assistant configuration files. Versions prior to 2.5.2 write SSH private-key material to a file under the Home Assistant configuration directory before applying restrictive permissions. The implementation in custom_components/blueprint_studio/backend/terminal_manager.py relies on best-effort cleanup, so the key can temporarily remain readable on disk. If cleanup fails or Home Assistant crashes, the private key persists. Any user or process with filesystem access to the configuration directory can retrieve the residual credential. The issue is tracked as [CWE-522: Insufficiently Protected Credentials] and is fixed in version 2.5.2.

Critical Impact
A local actor with read access to the Home Assistant configuration directory can recover an SSH private key and reuse it to authenticate against downstream systems.

Affected Products

Blueprint Studio versions prior to 2.5.2
Home Assistant deployments using the blueprint_studio custom component
Systems exposing the Home Assistant configuration directory to non-root users or shared processes

Discovery Timeline

2026-08-18 - CVE-2026-53456 published to NVD
2026-08-19 - Last updated in NVD database

Technical Details for CVE-2026-53456

Vulnerability Analysis

Blueprint Studio provides an in-browser terminal that authenticates SSH sessions using key-based authentication. To pass the key material to the underlying SSH client, terminal_manager.py writes the private key to a file inside the Home Assistant configuration directory. The write occurs before the file mode is tightened to 0600, creating a race window in which any local reader can access the file with default permissions. The component then depends on best-effort cleanup to remove the file after the session ends.

Because cleanup runs only on the happy path, a Home Assistant crash, container restart, or unhandled exception leaves the key persisted on disk. The Home Assistant configuration directory is commonly readable by add-on containers, backup jobs, and administrative helpers, expanding the set of subjects able to exfiltrate the credential.

Root Cause

The root cause is an ordering flaw combined with reliance on non-atomic cleanup. Writing key material before restricting permissions violates the principle of least privilege for credential handling, and the absence of a finally-guarded removal path means residual data survives abnormal termination.

Attack Vector

Exploitation requires local filesystem access to the Home Assistant configuration directory. An attacker with a low-privileged shell, a co-located add-on, or read access to a backup archive can retrieve the private key and reuse it against any SSH endpoint the operator configured through Blueprint Studio.

python

# Patch excerpt: custom_components/blueprint_studio/backend/git_manager.py
import re
import shutil
import subprocess
import tempfile
from pathlib import Path
from typing import Any

Source: GitHub Commit 943aed0

python

# Patch excerpt: custom_components/blueprint_studio/backend/api.py
_ADMIN_ONLY_ACTIONS = frozenset({
    "call_service",
    "delete",
    "delete_multi",
    "global_replace",
    "git_force_push",
    "git_hard_reset",
    "git_delete_repo",
    "git_delete_remote_branch",
    "render_template",
    "restart_home_assistant",
})

Source: GitHub Commit 943aed0. The fix moves temporary credential handling to Python's tempfile module and expands the admin-only action list to reduce the attack surface reachable from non-admin sessions.

Detection Methods for CVE-2026-53456

Indicators of Compromise

Presence of files matching SSH private-key headers (-----BEGIN OPENSSH PRIVATE KEY-----, -----BEGIN RSA PRIVATE KEY-----) inside the Home Assistant configuration directory.
Residual files created by terminal_manager.py that were not removed after a Home Assistant restart or crash.
Unexpected SSH authentications to downstream hosts from Home Assistant's outbound IP using keys previously staged by Blueprint Studio.

Detection Strategies

Scan the Home Assistant configuration directory recursively for private-key material and correlate hits with Blueprint Studio installations below version 2.5.2.
Audit process and container file access logs for reads of paths under custom_components/blueprint_studio/ by identities other than the Home Assistant service account.
Review authentication logs on servers targeted by Blueprint Studio terminals for key-based logins outside expected maintenance windows.

Monitoring Recommendations

Enable filesystem integrity monitoring on the Home Assistant configuration directory to alert on new files with private-key signatures.
Forward Home Assistant and add-on container logs to a centralized store and alert on Blueprint Studio session errors that indicate incomplete cleanup.
Track SSH key fingerprints used for outbound sessions and rotate any key that Blueprint Studio may have handled prior to patching.

How to Mitigate CVE-2026-53456

Immediate Actions Required

Upgrade Blueprint Studio to version 2.5.2 or later on every Home Assistant instance running the custom component.
Rotate every SSH private key that was ever configured for use with Blueprint Studio terminals, and revoke the corresponding public keys on destination hosts.
Search the Home Assistant configuration directory for residual key files and securely delete any matches.

Patch Information

The fix is available in Blueprint Studio Release v2.5.2. The remediation is described in GitHub Security Advisory GHSA-3vg8-xf27-7q45 and implemented in commit 943aed0. The patch relocates private-key handling to Python's tempfile facilities and enforces admin-only access on sensitive backend actions.

Workarounds

Restrict filesystem permissions on the Home Assistant configuration directory so that only the Home Assistant service account can read its contents.
Disable the Blueprint Studio terminal feature until the upgrade to 2.5.2 is complete.
Avoid storing production SSH keys in Home Assistant; use short-lived certificates or dedicated jump hosts where feasible.

bash

# Verify the installed Blueprint Studio version and remove residual key files
grep -R "version" /config/custom_components/blueprint_studio/manifest.json
find /config -type f -exec grep -lE "BEGIN (OPENSSH|RSA|EC|DSA) PRIVATE KEY" {} \;
# After confirming, upgrade to 2.5.2 and rotate all impacted SSH keys