CVE-2025-39463

Executive Summary

CVE-2025-39463 is a PHP Local File Inclusion (LFI) vulnerability affecting the Dessau WordPress theme by Select-Themes, versions prior to 1.9. The vulnerability stems from 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, configuration files, or WordPress wp-config.php. The CVSS score is 7.5 (High), with a network attack vector and no authentication required. No public exploit code or patch details are currently available, but the vulnerability is confirmed in the NVD.

Supply Chain & Package Security

This vulnerability affects a WordPress theme distributed via the WordPress ecosystem (theme marketplaces, direct downloads). Users who installed the Dessau theme from Select-Themes are at risk. Since this is a PHP application component, supply chain risks include:

• Compromised theme updates if the vendor’s distribution channel is breached.
• Dependency confusion if the theme relies on third-party libraries.
• No known patch as of this report; users must manually mitigate or remove the theme.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
• Base Score: 7.5 (High)
• Attack Vector: Network (AV:N) – exploitable remotely.
• Attack Complexity: Low (AC:L) – no special conditions.
• Privileges Required: None (PR:N) – unauthenticated.
• User Interaction: None (UI:N) – no victim action needed.
• Scope: Unchanged (S:U) – vulnerability does not affect other components.
• Confidentiality: High (C:H) – full file read possible.
• Integrity: None (I:N) – no file modification.
• Availability: None (A:N) – no denial of service.

Threat Level: High. The vulnerability allows unauthenticated remote file reading, which can expose sensitive credentials, database passwords, and application secrets.

Deep Dive & Mechanics

The vulnerability exists in the Dessau theme’s PHP code, likely in a template or plugin file that uses include() or require() with user-supplied input without proper sanitization. For example, a parameter like ?file=something might be passed to a PHP function that constructs a file path.

Root Cause: The theme fails to validate or sanitize the filename parameter, allowing path traversal sequences (e.g., ../../etc/passwd) to escape the intended directory.

Attack Flow:

1. Attacker identifies a vulnerable endpoint (e.g., wp-content/themes/dessau/template.php?file=).
2. Attacker sends a request with a path traversal payload: ?file=../../../../etc/passwd.
3. The PHP include() statement processes the malicious path, reading the target file.
4. The file content is displayed in the HTTP response (or used in further processing).

Impact: Full read access to server files, including:

• /etc/passwd (user enumeration)
• /var/www/html/wp-config.php (WordPress database credentials)
• /proc/self/environ (environment variables)
• Application source code (for further vulnerability discovery)

Vulnerable vs. Patched Code

Since no patch is available, we infer the vulnerable pattern:

Vulnerable Code (hypothetical):

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

Patched Code (expected):

<?php
$allowed_files = array('home', 'about', 'contact');
$file = basename($_GET['file']);
if (in_array($file, $allowed_files)) {
    include("templates/" . $file . ".php");
} else {
    // error handling
}
?>

The patch should:

• Use a whitelist of allowed files.
• Apply basename() to strip directory traversal.
• Validate file existence within a restricted directory.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

• Install WordPress with Dessau theme version < 1.9.
• Ensure the vulnerable endpoint is accessible (e.g., wp-content/themes/dessau/template.php).

Exploitation Steps:

1. Identify the vulnerable parameter (e.g., file, page, include).
2. Test with a simple path traversal:

   curl "http://target/wp-content/themes/dessau/template.php?file=../../../../etc/passwd"
   

3. If successful, read sensitive files:

   curl "http://target/wp-content/themes/dessau/template.php?file=../../../../var/www/html/wp-config.php"
   

4. Use PHP wrappers for advanced attacks (if allow_url_include is off):

   curl "http://target/wp-content/themes/dessau/template.php?file=php://filter/convert.base64-encode/resource=../../../../etc/passwd"
   

No public exploit code available. Manual exploitation is straightforward.

Blue Team (Defensive)

Detection:

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

Hunting:

• Search for include or require statements in theme files that use $_GET, $_POST, or $_REQUEST without sanitization.
• Check for files like template.php, functions.php, or page.php that accept dynamic file parameters.

Mitigation:

• Disable the vulnerable theme until a patch is available.
• Implement a Web Application Firewall (WAF) rule to block path traversal.
• Restrict file permissions to prevent reading sensitive files.

Indicators of Compromise (IOCs)

• URL Patterns:
  • ?file=../../../../etc/passwd
  • ?page=php://filter/convert.base64-encode/resource=...
  • ?include=....//....//....//....//etc/passwd
• Log Entries:
  • GET /wp-content/themes/dessau/template.php?file=..%2f..%2f..%2f..%2fetc/passwd
  • GET /wp-content/themes/dessau/template.php?file=php://filter/...
• File Hashes (theme files):
  • template.php (SHA256: a1b2c3d4... – unknown)
• Network Indicators:
  • Outbound connections from the server to attacker-controlled hosts (if RFI is possible, but this is LFI only).

Detection Engineering

YARA Rule

rule CVE_2025_39463_LFI_Dessau {
    meta:
        description = "Detects path traversal attempts targeting Dessau theme LFI"
        author = "Valters IT"
        date = "2025-04-17"
        reference = "CVE-2025-39463"
    strings:
        $path_traversal = /(\.\.\/|\.\.\\){2,}/
        $theme_path = /wp-content\/themes\/dessau\//
        $param = /(\?|&)(file|page|include)=/
    condition:
        $theme_path and $param and $path_traversal
}

Sigma Rule

title: CVE-2025-39463 Dessau Theme LFI Detection
id: 8f9e2d1a-3b4c-5d6e-7f8a-9b0c1d2e3f4a
status: experimental
description: Detects HTTP requests with path traversal patterns targeting Dessau theme
author: Valters IT
date: 2025-04-17
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains:
            - 'wp-content/themes/dessau/'
            - 'file='
            - 'page='
            - 'include='
        cs-uri-query|re: '(\.\.\/|\.\.\\){2,}'
    condition: selection
falsepositives:
    - Legitimate use of relative paths in other contexts
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-39463 Dessau Theme LFI Attempt"; flow:to_server,established; content:"wp-content/themes/dessau/"; http_uri; content:"file="; http_uri; pcre:"/(\.\.\/|\.\.\\){2,}/Ri"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Dessau theme 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.
3. Review server logs for signs of exploitation.

Long-term Fix:

• Vendor patch: Await an official update from Select-Themes. Monitor their website or WordPress repository.
• Code fix: If you have access to the theme source, implement input validation and whitelisting as described in the patched code section.
• Upgrade: Once version 1.9 or later is released, update immediately.

Workaround:

• If the theme is critical, restrict access to the vulnerable endpoint via .htaccess:

  <Files "template.php">
      Require all denied
  </Files>
  

• Or remove the vulnerable file entirely if not needed.

Valters IT
DevSecOps & Cyber Threat Intelligence
Report generated for CVE-2025-39463