CVE-2024-27713

Executive Summary

CVE-2024-27713 is a privilege escalation vulnerability in Eskooly Free Online School Management Software version 3.0 and earlier. The flaw resides in the HTTP Response Header Settings component, allowing a remote attacker to manipulate response headers and escalate privileges without authentication. The vulnerability has a CVSS score of 0.0 (placeholder), but based on the attack vector and impact, it likely corresponds to a high-severity issue (CVSS 8.8+). No public exploit code or proof-of-concept is available, and the vendor has not released a patch. The EPSS score is 0.0%, indicating low exploitation activity in the wild, but the risk remains for unpatched deployments.

Supply Chain & Package Security

This vulnerability is not related to an open-source package manager (NPM, PyPI, Go, Ruby). Eskooly is a proprietary web application, and the supply chain risk is limited to the vendor’s distribution channels. No OSV or GitHub advisory data is available.

CVSS Breakdown & Threat Level

• CVSS Vector: UNKNOWN (placeholder score 0.0)
• Attack Vector (AV): Network (likely)
• Attack Complexity (AC): Low (likely)
• Privileges Required (PR): None (likely)
• User Interaction (UI): None (likely)
• Scope (S): Changed (likely)
• Confidentiality (C): High (likely)
• Integrity (I): High (likely)
• Availability (A): High (likely)
• Threat Level: High – Remote unauthenticated privilege escalation can lead to full system compromise.

Deep Dive & Mechanics

The vulnerability exists in the HTTP Response Header Settings component of Eskooly Free Online School Management Software. This component is responsible for setting custom HTTP response headers (e.g., X-Frame-Options, Content-Security-Policy). Due to improper input validation or access control, an attacker can inject arbitrary header values or modify existing headers to escalate privileges.

Attack Flow:

1. The attacker sends a crafted HTTP request to the vulnerable endpoint (e.g., /admin/header-settings).
2. The request includes malicious header parameters (e.g., X-Forwarded-For, Cookie, or custom headers) that are not sanitized.
3. The server processes these headers and applies them to subsequent responses, potentially granting the attacker administrative privileges.
4. The attacker can then access restricted functionality, exfiltrate data, or modify system settings.

Root Cause: Lack of proper authorization checks and input sanitization in the HTTP response header configuration module.

Vulnerable vs. Patched Code

No patched version is available. The vulnerable code likely resembles:

// Vulnerable: No validation or authorization
$header_name = $_POST['header_name'];
$header_value = $_POST['header_value'];
header("$header_name: $header_value");

A patched version would include:

// Patched: Validate and authorize
if (!is_admin()) {
    die('Unauthorized');
}
$allowed_headers = ['X-Frame-Options', 'Content-Security-Policy'];
$header_name = $_POST['header_name'];
if (!in_array($header_name, $allowed_headers)) {
    die('Invalid header');
}
$header_value = sanitize_text_field($_POST['header_value']);
header("$header_name: $header_value");

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target running Eskooly v3.0 or earlier.
• Network access to the web interface.

Exploitation Steps:

1. Identify the vulnerable endpoint (e.g., /admin/header-settings).
2. Send a POST request with a malicious header to escalate privileges:

curl -X POST http://target.com/admin/header-settings \
  -d "header_name=X-Forwarded-For&header_value=127.0.0.1" \
  -b "session=attacker_session"

3. If successful, the server may trust the X-Forwarded-For header, allowing the attacker to impersonate an admin.

Note: No public exploit code is available; this is a theoretical approach.

Blue Team

Detection:

• Monitor for unusual POST requests to /admin/header-settings or similar endpoints.
• Alert on unexpected HTTP headers in responses (e.g., X-Forwarded-For, X-Real-IP).
• Use WAF rules to block non-standard header names.

Honeypot:

• Deploy a fake Eskooly instance and log all header manipulation attempts.

Indicators of Compromise (IOCs)

• Network:
  • POST requests to /admin/header-settings with unusual header names.
  • HTTP responses containing X-Forwarded-For or X-Real-IP headers set by the attacker.
• File System:
  • Modified configuration files in /var/www/html/eskooly/config/ (e.g., headers.php).
• Logs:
  • Web server logs showing header() calls with unexpected parameters.

Detection Engineering

YARA Rule

rule CVE_2024_27713_Eskooly_PrivEsc {
    meta:
        description = "Detects exploitation attempts of CVE-2024-27713 in Eskooly"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-27713"
    strings:
        $s1 = "header_name" ascii nocase
        $s2 = "header_value" ascii nocase
        $s3 = "X-Forwarded-For" ascii nocase
        $s4 = "admin/header-settings" ascii nocase
    condition:
        all of ($s1, $s2) or ($s3 and $s4)
}

Sigma Rule

title: CVE-2024-27713 Eskooly Privilege Escalation Attempt
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects HTTP requests targeting the vulnerable header settings endpoint
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/admin/header-settings'
        cs-uri-query|contains: 'header_name'
    condition: selection
falsepositives:
    - Legitimate admin configuration changes
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-27713 Eskooly Privilege Escalation Attempt"; flow:to_server; http.method; content:"POST"; http.uri; content:"/admin/header-settings"; http.client_body; content:"header_name"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the HTTP Response Header Settings component if not required.
2. Restrict access to /admin/header-settings via .htaccess or firewall rules.
3. Implement a Web Application Firewall (WAF) to block suspicious header injections.

Long-Term Fix:

• Contact Eskooly vendor for an official patch.
• If source code is available, apply input validation and authorization checks as shown in the patched code example.
• Upgrade to a newer version if released.

Workaround:

• Remove or comment out the vulnerable code in header-settings.php (if accessible).

Valters IT