FlowiseAI/Flowise has Server-Side Request Forgery (SSRF) vulnerability

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)

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

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 '.'

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.