CVE-2026-71268 — OpenPLC Runtime v3's compile_program() function (webserver/openplc.py) parses…¶

Key facts

CVE-2026-71268 is a Critical (9.9) vulnerability: OpenPLC Runtime v3's compile_program() function (webserver/openplc.py) parses…. This entry ships a detection-only PoC and a Docker test lab.


CVE	CVE-2026-71268
Severity	Critical (9.9)
Detection / prevention	—
PoC	poc.py
Source	2026/CVE-2026-71268/

Details¶

English | 한국어

Description¶

OpenPLC Runtime v3's compile_program() function (webserver/openplc.py) parses (*FILE:path content*) directives from uploaded Structured Text (.st) program files and writes the referenced content to os.path.join('./core', file_path) with no validation that file_path stays within the ./core directory. A crafted .st file containing a directive such as (*FILE:../../../etc/cron.d/x * * * * root <command>*) writes attacker-controlled content to an arbitrary filesystem path, enabling remote code execution (e.g. via cron or SSH authorized_keys). A path-validation function, validate_file_path(), exists elsewhere in the codebase (webserver/credentials.py) but is never invoked from compile_program(), leaving the sink unprotected. OpenPLC additionally ships with hardcoded default credentials (openplc:openplc), lowering the practical bar for exploitation.

Vulnerability Details¶

Property	Value
CVE ID	CVE-2026-71268
Type	RCE
CVSS Score	9.9

Proof of Concept¶

Download¶

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-71268/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-2026-71268

# 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/thiagoralves/OpenPLC_v3
https://github.com/thiagoralves/OpenPLC_v3/blob/master/webserver/openplc.py

Generated by PoC Generator on 2026-08-09T21:07:30.438422761

Frequently asked questions¶

What is CVE-2026-71268?¶

CVE-2026-71268 is a Critical (9.9) vulnerability: OpenPLC Runtime v3's compile_program() function (webserver/openplc.py) parses…. This entry ships a detection-only PoC and a Docker test lab.

How do I detect CVE-2026-71268?¶

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-2026-71268?¶

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.