avergnaud/next.js_exploit_cve-2024-34351Educational demo of a Server-Side Request Forgery (SSRF) vulnerability in Next.js (CVE-2024-34351), with step-by-step exploitation and mitigation examples.
This repo can be used as support to present one or more meetup(s). The path is as follows...
This work is mainly based on two sources:
1-csr-load-data vanilla react SPA loading data
[!IMPORTANT] CSR (Client-Side Rendering): React code is delivered to the browser, which generates content that is inserted into the DOM.
cd 1-csr-load-data
npm start
2-csr-router vanilla react SPA routing[!IMPORTANT] After the page has been loaded for the first time, navigating to other pages on the same website uses JavaScript to re-render parts of the page without requiring a full page refresh.
cd 2-csr-router
npm start
3-rsc-load-data React Server Components (Next.js impl) loading data
[!IMPORTANT] React components which are written to run only on the server, rather than in the browser.
cd 3-rsc-load-data
npm run build
npm run start
4-rsc-router React Server Components (Next.js impl) routing
[!IMPORTANT] Components are executed only on the server. The default behavior is static rendering: components are executed at build time.
cd 4-rsc-router
npm run build
npm run start
5-SSR SSR Server Side Rendering
[!IMPORTANT] SSR means prerendering client components on the server. React code runs at the time it is requested. The result may be cached for future requests.
Best practice: define 'use client'; components as far down the component tree as possible.
[!IMPORTANT] "In React, “hydration” is how React “attaches” to existing HTML that was already rendered by React in a server environment. During hydration, React will attempt to attach event listeners to the existing markup and take over rendering the app on the client. In apps fully built with React, you will usually only hydrate one “root”, once at startup for your entire app."
cd 5-ssr
npm run build
npm run start
6-pages-router-ssg (Next.js impl)
[!IMPORTANT] SSG (Static Site Generation) using the pages router: React code is run when you build your application, and the generated output is static.
cd 6-pages-router-ssg
npm run build
npm run start
7-pages-router-isr (Next.js impl)
[!IMPORTANT] ISR (using pages router): "Next.js allows you to create or update static pages after you’ve built your site. Incremental Static Regeneration (ISR) enables you to use static-generation on a per-page basis, without needing to rebuild the entire site. With ISR, you can retain the benefits of static while scaling to millions of pages."
cd 7-pages-router-isr
npm run build
npm run start
"the data could become stale at request time"
...
8-ssrf-14.1.0
14.1.1redirect(/blog/${inputValue});Next.JS executes the request server-side, then returns the result to the browser:
redirect('/blog/123'); function constructs the URL http://207.154.209.99/blog/123.
To construct this URL, Next.JS notably retrieves the host 207.154.209.99 from the HTTP header of the initial request.Content-Type: text/x-component header, then Next.JS queries the URL with an HTTP GET.
To achieve an SSRF on the target server, we must therefore run another server:
Content-Type: text/x-component header, for any HEAD request
8-ssrf-14.1.0In /etc/nginx/sites-available/nextjs
Before:
server {
listen 80 default_server;
location / {
proxy_pass http://localhost:3000;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
}
After:
server {
listen 80;
server_name 207.154.209.99;
location / {
proxy_pass http://localhost:3000;
proxy_set_header Host 207.154.209.99;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
}
Risk of side effects...
Pages in the app directory are Server Components by default. This is different from the pages directory where pages are Client Components.
Upgrading to Next.js 13 does not require using the new App Router. You can continue using pages with new features that work in both directories
If we want to compare loading performance for the different solutions, we can add web core vital metrics in console.log.
ISR using App router ?
In the Next.js App Router, all fetched data is now static by default, rendered at build time. However, this can be changed easily: Next.js extends the fetch options object to provide flexibility in caching and revalidating rules. You can use the {next: {revalidate: number}} option to refresh static data at set intervals or when backend changes occur (Incremental Static Regeneration), while the {cache: 'no-store'} option can be passed in the fetch request for dynamic data (server-side rendering).