CVE-2025-54689

Executive Summary

CVE-2025-54689 is a critical PHP Local File Inclusion (LFI) vulnerability discovered in the Urna WordPress theme developed by Thembay. The flaw resides in improper control of filenames used in PHP include/require statements, allowing an unauthenticated attacker to include arbitrary local files from the server. This can lead to sensitive information disclosure, such as reading /etc/passwd, WordPress configuration files (wp-config.php), or other system files. The vulnerability affects all versions of Urna up to and including 2.5.7. No patch is currently available, and no public proof-of-concept (PoC) code has been released.

Supply Chain & Package Security

This vulnerability is specific to the WordPress ecosystem as a theme component. The Urna theme is distributed via WordPress theme repositories and third-party marketplaces. Users who have installed this theme from untrusted sources may be at higher risk. No official patch has been released by Thembay, and the theme may be abandoned. Organizations should treat this as a supply chain risk and consider replacing the theme.

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: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: None
• Availability Impact: None

The vulnerability is easily exploitable remotely without authentication, making it a high-priority threat for any site using the Urna theme.

Deep Dive & Mechanics

The Urna theme improperly sanitizes user-supplied input used in PHP include or require statements. This is a classic Local File Inclusion (LFI) vulnerability. The vulnerable code likely appears in a template or function that accepts a file parameter (e.g., via $_GET['file'] or $_POST['file']) and passes it directly to include() without proper validation or path sanitization.

Example vulnerable code pattern:

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

An attacker can exploit this by providing a path traversal sequence (e.g., ../../../../etc/passwd%00) to include arbitrary files. The null byte (%00) may be used to terminate the string and bypass the .php extension append.

Attack flow:

1. Attacker sends a crafted HTTP request to a vulnerable endpoint.
2. The request includes a file parameter with path traversal.
3. The server includes the specified file, outputting its contents.
4. Sensitive data is disclosed.

Vulnerable vs. Patched Code

Since no patch is available, we can only hypothesize the vulnerable code and a potential fix.

Vulnerable code (hypothetical):

// In a theme template file (e.g., header.php)
$template = $_GET['template'];
include(get_template_directory() . '/templates/' . $template . '.php');

Patched code (recommended):

// Use a whitelist of allowed files
$allowed_templates = array('header', 'footer', 'sidebar');
$template = $_GET['template'];
if (in_array($template, $allowed_templates)) {
    include(get_template_directory() . '/templates/' . $template . '.php');
} else {
    // Handle error
    wp_die('Invalid template.');
}

The patched version validates the input against a whitelist, preventing arbitrary file inclusion.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A WordPress instance with Urna theme <= 2.5.7 installed.
• Knowledge of the vulnerable endpoint (e.g., /wp-content/themes/urna/some-page.php?file=...).

Exploitation steps:

1. Identify the vulnerable parameter (likely file, template, or include).
2. Send a request to read /etc/passwd:

   GET /wp-content/themes/urna/vulnerable-file.php?file=../../../../etc/passwd%00 HTTP/1.1
   Host: target.com
   

3. If successful, the response will contain the contents of /etc/passwd.
4. To read wp-config.php:

   GET /wp-content/themes/urna/vulnerable-file.php?file=../../../../wp-config%00 HTTP/1.1
   

Note: No public exploit code is available. The above is a generic LFI exploitation technique.

Blue Team (Defensive)

Detection:

• Monitor web server logs for path traversal patterns (e.g., ../, %00, %2e%2e%2f).
• Look for requests to theme files with suspicious parameters.
• Use WAF rules to block LFI attempts.

Hunting:

• Search for include or require statements in the Urna theme code that use user input.
• Check for any recent modifications to theme files.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP requests containing ../ or %00 in parameters.
  • Requests to /wp-content/themes/urna/ with unusual file parameters.
  • Outbound connections from the server to unknown IPs (if RFI is also possible).

• File IOCs:

  • Unexpected files in /tmp/ or web root.
  • Modified theme files (e.g., backdoored functions.php).

• Log IOCs:

  • Web server logs showing 404 errors for non-existent files.
  • PHP error logs with include() failures.

Detection Engineering

YARA Rule

rule CVE_2025_54689_LFI_Urna {
    meta:
        description = "Detects LFI attempts targeting Urna WordPress theme"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-54689"
    strings:
        $path_traversal = /(\.\.\/|\.\.\\){2,}/
        $null_byte = /\x00/
        $wp_config = /wp-config\.php/i
        $passwd = /etc\/passwd/i
    condition:
        any of ($path_traversal) and any of ($null_byte, $wp_config, $passwd)
}

Sigma Rule

title: CVE-2025-54689 LFI Attempt on Urna Theme
id: 8a7b3c2d-1e4f-5a6b-7c8d-9e0f1a2b3c4d
status: experimental
description: Detects path traversal attempts targeting the Urna WordPress theme
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-uri-query|contains:
            - '../'
            - '..\\'
            - '%2e%2e%2f'
            - '%00'
        cs-uri-stem|contains: '/wp-content/themes/urna/'
    condition: selection
falsepositives:
    - Legitimate use of relative paths in theme files (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-54689 LFI Attempt on Urna Theme"; flow:to_server,established; content:"/wp-content/themes/urna/"; http_uri; content:"../"; http_uri; distance:0; content:"%00"; http_uri; distance:0; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate actions:

1. Disable or replace the Urna theme with a secure alternative.
2. Apply a virtual patch using a Web Application Firewall (WAF) to block LFI patterns.
3. Restrict file permissions on sensitive files (e.g., wp-config.php should be 600).

Long-term fixes:

• The vendor (Thembay) must release a patched version that sanitizes file inputs.
• If the theme is abandoned, consider migrating to a maintained theme.
• Implement input validation and whitelisting for all file inclusion operations.

Workaround:

• Add the following to .htaccess to block common LFI patterns:

  RewriteEngine On
  RewriteCond %{QUERY_STRING} (\.\.\/|%00) [NC]
  RewriteRule .* - [F,L]
  

Valters IT
Securing Digital Frontiers