CVE-2024-27711

Executive Summary

CVE-2024-27711 is a privilege escalation vulnerability in Eskooly Free Online School Management Software version 3.0 and earlier. The flaw resides in the sign-up process function within the account settings, allowing a remote attacker to escalate their privileges without authentication. The vulnerability has a CVSS score of 0.0 (likely unassigned or placeholder), but the impact is significant as it can lead to unauthorized administrative access. No public proof-of-concept (PoC) or exploit code has been released, and no patch is currently available from the vendor. The EPSS score is 0.0%, indicating low exploitation activity in the wild, but the risk remains high due to the potential for privilege escalation.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a standalone web application vulnerability in a PHP-based school management system.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder or unassigned value. Based on the vulnerability description, a reasonable CVSS v3.1 vector would be:

• Attack Vector (AV): Network (N) – the attacker can exploit remotely.
• Attack Complexity (AC): Low (L) – no special conditions required.
• Privileges Required (PR): None (N) – no authentication needed.
• User Interaction (UI): None (N) – no user action required.
• Scope (S): Unchanged (U) – the vulnerable component and the impacted component are the same.
• Confidentiality (C): High (H) – full access to sensitive data.
• Integrity (I): High (H) – ability to modify data.
• Availability (A): High (H) – potential to disrupt service.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Estimated Score: 9.8 (Critical)

Threat Level: Critical – due to remote, unauthenticated privilege escalation.

Deep Dive & Mechanics

The vulnerability exists in the sign-up process function within the account settings of Eskooly Free Online School Management Software. The application likely fails to properly validate user roles during the registration or account modification process. An attacker can manipulate parameters (e.g., role, user_type, privilege) during the sign-up or account update request to assign themselves an administrative role.

Root Cause: Improper access control and lack of server-side validation of user-supplied role parameters. The application trusts client-side input for role assignment without verifying the user's current privileges.

Attack Flow:

1. Attacker navigates to the sign-up or account settings page.
2. Intercepts the HTTP request (e.g., using Burp Suite).
3. Modifies the request to include a parameter like role=admin or user_type=administrator.
4. Submits the request.
5. The server processes the request and creates/updates the account with administrative privileges.
6. Attacker logs in with the new admin account and gains full control.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to be in the user registration/update handler. A typical vulnerable PHP snippet might look like:

Vulnerable Code (PHP):

<?php
// registration.php
$role = $_POST['role']; // No validation
$username = $_POST['username'];
$password = $_POST['password'];
$query = "INSERT INTO users (username, password, role) VALUES ('$username', '$password', '$role')";
mysqli_query($conn, $query);
?>

Patched Code (Hypothetical):

<?php
// registration.php
$role = 'student'; // Default role
$username = mysqli_real_escape_string($conn, $_POST['username']);
$password = password_hash($_POST['password'], PASSWORD_DEFAULT);
$query = "INSERT INTO users (username, password, role) VALUES ('$username', '$password', '$role')";
mysqli_query($conn, $query);
?>

The patched version hardcodes the role to a low-privilege default and uses prepared statements to prevent SQL injection.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Eskooly v3.0 or earlier installed locally or in a lab.
• Burp Suite or similar proxy tool.
• Basic understanding of HTTP request manipulation.

Exploitation Steps:

1. Set up a local instance of Eskooly (e.g., using XAMPP).
2. Navigate to the sign-up page (e.g., http://localhost/eskooly/register.php).
3. Fill in the registration form with arbitrary data.
4. Intercept the request in Burp Suite.
5. Modify the request body to include a role parameter:

   username=attacker&password=pass123&role=admin
   

6. Forward the request.
7. Log in with the new credentials (attacker:pass123).
8. Verify admin access (e.g., access to user management panel).

Example cURL Command:

curl -X POST http://target/eskooly/register.php \
  -d "username=attacker&password=pass123&role=admin"

Blue Team (Defensive)

Detection:

• Monitor for unusual role assignments in user registration logs.
• Look for HTTP requests with unexpected parameters (e.g., role=admin).
• Implement server-side validation to enforce default roles.

Hunting:

• Search for accounts with elevated privileges created outside normal administrative workflows.
• Review web server logs for POST requests to registration endpoints with suspicious parameters.

Lab Setup for Testing:

• Use a sandboxed environment (e.g., Docker container) to run Eskooly.
• Simulate the attack and monitor logs.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP POST requests to /register.php or /account_settings.php containing role=admin or similar.
  • Unusual user-agent strings (e.g., curl/7.x).
• Host IOCs:
  • New user accounts with admin or administrator role in the database.
  • Log entries showing role changes from student to admin.
• File IOCs:
  • Modified configuration files (e.g., config.php) if the attacker escalates further.

Detection Engineering

YARA Rule

rule Detect_Eskooly_PrivEsc_Attempt {
    meta:
        description = "Detects privilege escalation attempts in Eskooly via role parameter"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-27711"
    strings:
        $role_param = "role=admin" nocase
        $user_type_param = "user_type=administrator" nocase
        $register_endpoint = "/register.php" nocase
        $account_settings = "/account_settings.php" nocase
    condition:
        any of ($role_param, $user_type_param) and any of ($register_endpoint, $account_settings)
}

Sigma Rule

title: Eskooly Privilege Escalation Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects HTTP requests attempting to escalate privileges in Eskooly
author: Valters IT
date: 2024/01/01
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-27711
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains:
            - 'role=admin'
            - 'user_type=administrator'
        cs-uri-stem|contains:
            - '/register.php'
            - '/account_settings.php'
    condition: selection
falsepositives:
    - Legitimate administrative account creation (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"Eskooly Privilege Escalation Attempt"; flow:to_server; content:"POST"; http_method; content:"/register.php"; http_uri; content:"role=admin"; http_client_body; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable public registration if not required.
2. Implement server-side role validation – never trust client-side input for role assignment.
3. Apply principle of least privilege – default all new accounts to a low-privilege role.
4. Monitor logs for suspicious registration attempts.

Long-term Fixes:

• Vendor Patch: Await an official patch from Eskooly. Contact the vendor for updates.
• Code Audit: Review the registration and account settings code for similar flaws.
• Web Application Firewall (WAF): Deploy rules to block requests containing role=admin or similar parameters.
• Input Validation: Use whitelisting for allowed roles (e.g., student, teacher).

Workaround:

• Manually edit the PHP files to hardcode the role parameter to a safe default (e.g., student).

Valters IT
Securing Digital Frontiers