CVE-2025-55182 & CVE-2025-66478
LEGAL DISCLAIMER
EN: This tool is a Proof of Concept (PoC) intended for security research and educational purposes only. Using this tool on systems without explicit permission is illegal and punishable by law. The author (Tiger-Foxx) assumes no responsibility for misuse.
FR: Cet outil est une Preuve de Concept (PoC) destinée uniquement à la recherche en sécurité et à des fins éducatives. L'utilisation de cet outil sur des systèmes sans autorisation explicite est illégale.
DESCRIPTION
Fox-RSC Tool is a specialized browser extension and toolkit designed to detect and demonstrate the critical CVE-2025-55182 (React2Shell) vulnerability affecting React Server Components (RSC).
This toolkit provides a comprehensive suite for security researchers to identify vulnerable endpoints and verify the Remote Code Execution (RCE) vector in a controlled environment.
TECHNICAL ANALYSIS: CVE-2025-55182 (React2Shell)
Vulnerability Class: Insecure Deserialization / Remote Code Execution
CVSS Score: 10.0 (Critical)
Disclosure Date: December 3, 2025
Overview
Also known as React2Shell, this critical vulnerability affects the Flight protocol used by React Server Components (RSC), specifically within the
eact-server\ package. It allows for unauthenticated Remote Code Execution (RCE) with a CVSS score of 10.0.
Mechanism
The vulnerability stems from insecure deserialization of RSC payloads.
- Injection: An attacker crafts a malicious HTTP request containing a specific payload.
- Deserialization: When the server processes this request using the Flight protocol, it fails to properly validate the input.
- Execution: The deserialization process triggers the execution of arbitrary, privileged JavaScript code within the server's context.
Exploitability & Impact
- High Reliability: The exploit has a success rate nearing 100% in testing environments.
- Unauthenticated: No user credentials are required to trigger the RCE.
- Wild Exploitation: The CISA has added this to its Known Exploited Vulnerabilities (KEV) catalog. Active exploitation has been observed since December 5, 2025, involving threat actors targeting cloud credentials and deploying crypto-miners (e.g., XMRig).
Prerequisites for Exploitation
- The target application must utilize React Server Components (RSC) on the server side (e.g., Next.js in default production mode).
- Note: Even if the application does not explicitly define Server Functions endpoints, it remains vulnerable if RSC support is enabled.
- Attack Vector: Any exposed endpoint handled by the RSC server can be targeted with a specially crafted HTTP request. It functions on standard configurations without requiring code modifications.
Affected Versions
- React: 19.0, 19.1.0, 19.1.1, 19.2.0
- Next.js: Versions 14.3.0-canary.77+, 15.x, 16.x
- Other Frameworks: React Router, Vite (RSC plugin), Parcel (RSC plugin), Waku.
Note: Pure client-side applications (SPA) or those without RSC support are not affected.
FEATURES
1. Chrome Extension (Premium Dark Theme)
- Passive Detection: Automatically analyzes HTTP headers (e.g.,
sc,
ext-router-state-tree) and DOM elements to identify Next.js/RSC applications.
- Active Fingerprinting: Sends lightweight, non-destructive probes to confirm the presence of the Flight protocol.
- RCE Exploit Terminal: A built-in terminal interface to test command execution (e.g., \whoami, \ls -la) on authorized targets.
Fox-RSC Tool extension popup showing the main interface with detection and exploit sections.
Built-in command templates for testing RCE (whoami, pwd, etc.) in the exploit section.
2. Proxy Server (\extension_proxy.py)
- A Python-based middleware to bypass CORS (Cross-Origin Resource Sharing) restrictions, enabling the extension to communicate with remote targets during testing.
3. Shodan Scanner (\shodan_scanner.py)
- Automated reconnaissance script utilizing the Shodan API to identify potentially vulnerable hosts exposed to the public internet.
INSTALLATION
Browser Extension
- Navigate to \chrome://extensions/\ in your Chromium-based browser.
- Enable Developer mode.
- Click Load unpacked.
- Select the \xtension/\ directory from this repository.
- The Fox-RSC Tool icon will appear in your browser toolbar.
Fox-RSC Tool icon visible in the browser toolbar after installation.
Proxy Server (Recommended)
To ensure reliable exploitation testing without CORS interference:
\\ash
python extension_proxy.py
\
The server will listen on port \8765.
Shodan Scanner
Requires a valid Shodan API key.
\\ash
pip install shodan requests tqdm
python shodan_scanner.py
\\
Shodan scanner output displaying vulnerable hosts and scan results.
MITIGATION
Immediate patching is required for all affected systems.
- React: Update to version 19.0.1, 19.1.2, 19.2.1 or later.
- Next.js: Update to the latest stable release.
- Hosting Providers: Some providers have applied temporary mitigations, but code-level updates are mandatory.
CREDITS
Developed by Tiger-Foxx
Original Design & Research
Stay Safe, Stay Secure.
