CVE-2025-59558

Executive Summary

CVE-2025-59558 is a critical PHP Local File Inclusion (LFI) vulnerability affecting the Billey WordPress theme by ThemeMove, versions prior to 2.1.6. The flaw stems from improper control of filenames in include/require statements, allowing an unauthenticated attacker to include arbitrary local files from the server. This can lead to sensitive information disclosure, including configuration files, credentials, and source code. The vulnerability is classified under CWE-98 (Improper Control of Filename for Include/Require Statement in PHP Program) and carries a CVSS score of 8.1 (High). No public exploit code or proof-of-concept is currently available, and the vendor has not released a patch. Given the WordPress ecosystem context, this vulnerability poses a significant risk to sites running the Billey theme.

Supply Chain & Package Security

This vulnerability is specific to the Billey WordPress theme, a commercial product distributed via ThemeMove. As a WordPress theme, it is part of the WordPress ecosystem and is typically installed via the WordPress admin panel or manually uploaded. There is no associated NPM, PyPI, Go, or Ruby package. The risk is limited to direct installations of the theme; however, compromised theme updates or malicious forks could propagate the vulnerability.

CVSS Breakdown & Threat Level

• CVSS Score: 8.1 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

The high confidentiality impact reflects the ability to read arbitrary files, including wp-config.php (database credentials), /etc/passwd, and other sensitive data. The low attack complexity and no required privileges make this easily exploitable by remote attackers.

Deep Dive & Mechanics

The vulnerability exists in the Billey theme's PHP code, specifically in functions that handle file inclusion without proper sanitization. The theme likely uses a parameter (e.g., page, template, or file) to dynamically include PHP files. An attacker can manipulate this parameter to traverse directories and include arbitrary files.

Example vulnerable code pattern:

<?php
$file = $_GET['file'];
include($file . '.php');
?>

By sending a request like:

http://target.com/?file=../../../etc/passwd%00

The attacker can include /etc/passwd (null byte injection may work in older PHP versions) or use path traversal to read sensitive files.

The theme's version 2.1.6 likely introduced proper input validation, such as whitelisting allowed files or using realpath() to restrict inclusion to a specific directory.

Vulnerable vs. Patched Code

Vulnerable Code (pre-2.1.6):

<?php
// No input validation
$template = $_GET['template'];
include( get_template_directory() . '/templates/' . $template . '.php' );
?>

Patched Code (2.1.6+):

<?php
$allowed_templates = array('home', 'about', 'contact');
$template = $_GET['template'];
if (in_array($template, $allowed_templates)) {
    include( get_template_directory() . '/templates/' . $template . '.php' );
} else {
    // Default template
    include( get_template_directory() . '/templates/home.php' );
}
?>

The patched version uses a whitelist to restrict inclusion to predefined templates, preventing path traversal.

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Install WordPress with the Billey theme (version < 2.1.6) on a local server (e.g., XAMPP, Docker).
2. Ensure the vulnerable parameter (e.g., template) is exposed in a URL.

Exploitation Steps:

1. Identify the vulnerable parameter by analyzing the theme's source code or using fuzzing.
2. Craft a request to read /etc/passwd:

   http://target.com/?template=../../../etc/passwd%00
   

3. If null byte injection fails, try:

   http://target.com/?template=../../../etc/passwd
   

   (Note: PHP 5.3+ may require the file to exist with .php extension; use path truncation or other techniques.)

Example using cURL:

curl -v "http://target.com/?template=../../../etc/passwd%00"

Expected Output: The contents of /etc/passwd will be displayed if successful.

Blue Team

Detection:

• Monitor web server logs for suspicious template parameters containing ../ or %00.
• Use WAF rules to block path traversal patterns.

Hunting:

• Search for requests with template= followed by directory traversal sequences.
• Check for unusual file inclusion attempts in PHP error logs.

Indicators of Compromise (IOCs)

• URL Patterns: ?template=../../../etc/passwd, ?template=../../wp-config.php
• Log Entries: GET /?template=../../../etc/passwd HTTP/1.1 with 200 response
• File Access: Unauthorized reads of /etc/passwd, wp-config.php, or other sensitive files
• Network Traffic: Outbound connections from the server to attacker-controlled hosts (if combined with RFI)

Detection Engineering

YARA Rule

rule CVE_2025_59558_LFI_Detection {
    meta:
        description = "Detects attempts to exploit CVE-2025-59558 LFI in Billey theme"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-59558"
    strings:
        $traversal = /template=\.\.\/\.\.\/\.\.\// nocase
        $nullbyte = /template=.*%00/ nocase
        $sensitive = /template=.*(etc\/passwd|wp-config\.php|\.\.\/)/ nocase
    condition:
        any of them
}

Sigma Rule

title: CVE-2025-59558 Billey Theme LFI Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP requests attempting to exploit LFI in Billey WordPress theme
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: 
            - 'template=../'
            - 'template=..%2f'
            - 'template=%2e%2e%2f'
    condition: selection
falsepositives:
    - Legitimate use of template parameter with valid paths (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-59558 Billey Theme LFI Attempt"; flow:to_server,established; content:"GET"; http_method; content:"template="; http_uri; content:"../"; within:100; reference:cve,2025-59558; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Update the theme: Upgrade to Billey version 2.1.6 or later if available. If not, consider switching to an alternative theme.
2. Apply virtual patching: Use a Web Application Firewall (WAF) to block requests containing template= with path traversal sequences.
3. Disable the vulnerable functionality: If possible, remove or comment out the vulnerable include code in the theme files.

Long-term Measures:

• Implement input validation and whitelisting for all file inclusion parameters.
• Use realpath() to resolve and restrict file paths.
• Regularly audit third-party themes and plugins for vulnerabilities.
• Enable PHP open_basedir restrictions to limit file access.

Workaround:

• Add the following rule to .htaccess (Apache) to block malicious requests:

RewriteEngine On
RewriteCond %{QUERY_STRING} template=\.\./ [NC,OR]
RewriteCond %{QUERY_STRING} template=.*%00 [NC]
RewriteRule ^ - [F,L]

Valters IT
Securing Digital Frontiers