CVE-2025-39490

Executive Summary

CVE-2025-39490 is a critical PHP Local File Inclusion (LFI) vulnerability affecting the Backpack Traveler WordPress theme by Qodeinteractive (Mikado-Themes). The vulnerability exists in versions up to and including 2.10.2, allowing an unauthenticated attacker to include arbitrary local files via the include/require PHP functions. This can lead to sensitive file disclosure (e.g., wp-config.php), potential remote code execution if combined with file upload, and full site compromise. The CVSS score of 8.1 (High) reflects the ease of exploitation and high confidentiality impact. No public exploit code or patch is currently available, making this a zero-day threat for unpatched installations.

WordPress Ecosystem Context

This vulnerability is specific to the Backpack Traveler WordPress theme. It is not an Apache or Nginx issue. The theme’s improper handling of file inclusion parameters allows attackers to traverse directories and read arbitrary files on the server.

CVSS Breakdown & Threat Level

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

Threat Level: High. The vulnerability is trivial to exploit and can expose sensitive credentials and configuration files.

Deep Dive & Mechanics

The vulnerability stems from the theme’s use of PHP’s include() or require() functions with user-supplied input that is not properly sanitized. Specifically, the theme likely uses a parameter (e.g., page, template, or file) to load template files. An attacker can inject path traversal sequences (e.g., ../../) to include arbitrary files from the server.

Example vulnerable code pattern:

$template = $_GET['template'];
include( get_template_directory() . '/templates/' . $template . '.php' );

An attacker can supply ../../../../etc/passwd to read system files.

Impact:

• Read wp-config.php to obtain database credentials.
• Read /etc/passwd for user enumeration.
• Potentially achieve RCE if combined with a file upload vulnerability (e.g., log poisoning).

Vulnerable vs. Patched Code

Since no patch is available, we can only hypothesize the fix. The vulnerable code likely lacks input validation and path restriction.

Vulnerable Code (hypothetical):

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

Patched Code (expected):

$allowed_files = array( 'home', 'about', 'contact' );
$file = $_GET['file'];
if ( in_array( $file, $allowed_files ) ) {
    include( get_template_directory() . '/templates/' . $file . '.php' );
} else {
    // Error handling
}

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A WordPress site running Backpack Traveler theme <= 2.10.2.
• Knowledge of the vulnerable parameter (e.g., file, template, page).

Exploitation Steps:

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

   GET /?file=../../../../etc/passwd HTTP/1.1
   Host: target.com
   

3. For WordPress credentials:

   GET /?file=../../../../wp-config HTTP/1.1
   Host: target.com
   

Lab Setup:

• Use Docker to spin up a vulnerable WordPress instance:

  docker run -d --name wp-vuln -p 8080:80 wordpress:latest
  

• Install Backpack Traveler theme version 2.10.2 manually.
• Access http://localhost:8080/?file=../../../../etc/passwd.

Blue Team (Defensive)

Detection:

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

Mitigation:

• Immediately upgrade the theme if a patch becomes available.
• Implement a Web Application Firewall (WAF) rule to block path traversal.
• Disable PHP allow_url_include and allow_url_fopen if not needed.

Indicators of Compromise (IOCs)

• File Paths: /etc/passwd, /wp-config.php, /proc/self/environ
• URL Patterns: ?file=, ?template=, ?page= followed by ../ sequences.
• Log Entries: HTTP 200 responses to requests containing ../ in query parameters.
• Network: Outbound connections from the web server to attacker-controlled hosts (if RCE achieved).

Detection Engineering

YARA Rule

rule CVE_2025_39490_LFI_BackpackTraveler {
    meta:
        description = "Detects LFI attempts targeting Backpack Traveler theme"
        author = "Valters IT"
        date = "2025-04-01"
        reference = "CVE-2025-39490"
    strings:
        $path_traversal = /\.\.\/|\.\.\\|%2e%2e%2f|%2e%2e%5c/
        $theme_param = /(file|template|page)=/
    condition:
        $theme_param and $path_traversal
}

Sigma Rule

title: CVE-2025-39490 Backpack Traveler LFI Attempt
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects path traversal attempts in HTTP requests targeting Backpack Traveler theme
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains:
            - 'file='
            - 'template='
            - 'page='
        cs-uri-query|re: '\.\.\/|\.\.\\|%2e%2e%2f|%2e%2e%5c'
    condition: selection
falsepositives:
    - Legitimate use of relative paths in theme (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-39490 Backpack Traveler LFI Attempt"; flow:to_server,established; content:"GET"; http_method; content:"file="; http_uri; content:"../"; http_uri; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Disable the Backpack Traveler theme and switch to a default WordPress theme (e.g., Twenty Twenty-Four) until a patch is released.
2. WAF Rules: Deploy virtual patching via WAF to block path traversal patterns.
3. Server Hardening:
   • Set open_basedir in PHP to restrict file access.
   • Disable allow_url_include and allow_url_fopen.
   • Use read-only filesystem for web root where possible.
4. Monitoring: Enable detailed logging and alert on suspicious URI patterns.
5. Vendor Contact: Reach out to Qodeinteractive for patch status and timeline.

Valters IT
Securing Digital Frontiers