CVE-2026-71259 — ESPHome through 2026.7.0-dev contains an operator-precedence bug in the cv.url()…¶

Key facts

CVE-2026-71259 is a High (8.6) vulnerability: ESPHome through 2026.7.0-dev contains an operator-precedence bug in the cv.url()…. This entry ships a detection-only PoC and a Docker test lab.


CVE	CVE-2026-71259
Severity	High (8.6)
Detection / prevention	—
PoC	poc.py
Source	2026/CVE-2026-71259/

Details¶

English | 한국어

Description¶

ESPHome through 2026.7.0-dev contains an operator-precedence bug in the cv.url() validator in esphome/config_validation.py: if parsed.scheme and parsed.netloc or parsed.scheme == "file": return parsed.geturl(). Because and binds tighter than or, any file: URI passes validation regardless of netloc. This validator gates the url: field of the external_components YAML directive's git source schema, which is passed to git clone (git supports file:// natively). A crafted external_components block with url: "file:///attacker/repo" clones an attacker-controlled local path, which is then added to Python's import machinery via ESPHome's component loader, executing arbitrary Python code when the YAML configuration is processed (e.g. via esphome config/esphome run).

Vulnerability Details¶

Property	Value
CVE ID	CVE-2026-71259
Type	RCE
CVSS Score	8.6

Proof of Concept¶

Download¶

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-71259/poc.py

Usage¶

# Run PoC against target
python3 poc.py --target <TARGET_URL>

# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>

⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.

Test Lab¶

This repository includes a Docker-based test environment with both vulnerable and patched applications.

Quick Start¶

# Clone and navigate to CVE directory
cd CVE-2026-71259

# Start both applications
docker-compose up -d

# Run tests
./run-tests.sh    # Linux/Mac
./run-tests.ps1   # Windows PowerShell

Application Endpoints¶

Application	URL	Status
Vulnerable App	http://localhost:8080	Shows vulnerability
Patched App	http://localhost:8081	Demonstrates fix

Directory Structure¶

├── README.md           # English documentation
├── README_KO.md        # Korean documentation
├── poc.py              # PoC detection script
├── docker-compose.yml  # Container orchestration
├── run-tests.sh        # Linux/Mac test runner
├── run-tests.ps1       # Windows test runner
├── vulnerable-app/     # Vulnerable version
│   ├── app.py
│   ├── Dockerfile
│   └── requirements.txt
└── patched-app/        # Fixed version
    ├── app.py
    ├── Dockerfile
    └── requirements.txt

References¶

https://github.com/esphome/esphome
https://github.com/esphome/esphome/blob/dev/esphome/config_validation.py

Generated by PoC Generator on 2026-08-09T22:32:39.42253278

Frequently asked questions¶

What is CVE-2026-71259?¶

CVE-2026-71259 is a High (8.6) vulnerability: ESPHome through 2026.7.0-dev contains an operator-precedence bug in the cv.url()…. This entry ships a detection-only PoC and a Docker test lab.

How do I detect CVE-2026-71259?¶

Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.

How do I block or mitigate CVE-2026-71259?¶

Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.

For authorized security testing and research only. See the full source and NVD record.