CVE-2025-31525

Executive Summary

CVE-2025-31525 is a Missing Authorization vulnerability in the WP Mobile Bottom Menu WordPress plugin (slug: mobile-bottom-menu-for-wp) developed by WP Messiah. This flaw allows an unauthenticated attacker to exploit incorrectly configured access control security levels, potentially leading to unauthorized actions or data exposure. The vulnerability affects all versions up to and including 1.4.0. With a CVSS score of 4.3 (Medium), the risk is moderate but elevated due to the lack of a known patch and the widespread use of WordPress plugins.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin distributed via the official WordPress plugin repository. Users who installed the plugin via the WordPress dashboard or directly from the repository are affected. No official patch has been released, and the vendor's status is unknown, making this a supply chain risk for any site using the plugin. Organizations should treat this as a potential backdoor or unauthorized access vector.

CVSS Breakdown & Threat Level

• CVSS Score: 4.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: Low
• Availability Impact: None

The low EPSS score (0.0%) suggests limited active exploitation in the wild, but the missing authorization flaw could be chained with other vulnerabilities for greater impact.

Deep Dive & Mechanics

The vulnerability stems from missing authorization checks in the plugin's AJAX handlers or REST API endpoints. Specifically, the plugin fails to verify user capabilities before executing sensitive actions, such as modifying menu settings, updating options, or accessing protected data. An attacker can send crafted HTTP requests to these endpoints without authentication, leading to unauthorized configuration changes or data leakage.

The plugin likely registers AJAX actions without proper current_user_can() checks, allowing any visitor to trigger administrative functions. This is a classic case of Incorrectly Configured Access Control Security Levels (CWE-862).

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is as follows:

Vulnerable (<=1.4.0):

add_action('wp_ajax_nopriv_mobile_menu_save_settings', 'mobile_menu_save_settings');
function mobile_menu_save_settings() {
    // No capability check
    update_option('mobile_menu_settings', $_POST['settings']);
}

Patched (hypothetical):

add_action('wp_ajax_mobile_menu_save_settings', 'mobile_menu_save_settings');
function mobile_menu_save_settings() {
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized');
    }
    update_option('mobile_menu_settings', $_POST['settings']);
}

The patched version adds a capability check and removes the nopriv prefix to restrict access to authenticated administrators.

Exploitation & Lab Setup

Red Team

1. Reconnaissance: Identify WordPress sites using the plugin via Shodan dorks or Google dorking.
2. Exploit: Send a crafted POST request to the vulnerable AJAX endpoint:

   curl -X POST http://target.com/wp-admin/admin-ajax.php \
        -d 'action=mobile_menu_save_settings&settings[menu_items][0][title]=Malicious'
   

3. Post-Exploitation: Modify plugin settings to inject malicious JavaScript or redirect users to phishing pages.

Blue Team

1. Detection: Monitor for unusual AJAX requests to admin-ajax.php with action parameters related to the plugin (e.g., mobile_menu_*).
2. Honeypot: Deploy a fake WordPress instance with the vulnerable plugin and log all requests.
3. Mitigation: Disable the plugin immediately if no patch is available. Use a Web Application Firewall (WAF) to block requests to vulnerable endpoints.

Indicators of Compromise (IOCs)

• Network: HTTP POST requests to /wp-admin/admin-ajax.php with action=mobile_menu_save_settings or similar.
• File: Presence of the plugin directory /wp-content/plugins/mobile-bottom-menu-for-wp/.
• Log: WordPress debug logs showing unauthorized AJAX calls.
• Database: Modified wp_options table entries with mobile_menu_settings key.

Detection Engineering

YARA Rule

rule CVE_2025_31525_WordPress_Plugin {
    meta:
        description = "Detects WP Mobile Bottom Menu plugin files with missing authorization"
        author = "Valters IT"
        date = "2025-04-01"
        hash = "unknown"
    strings:
        $ajax_nopriv = "wp_ajax_nopriv_mobile_menu" nocase
        $missing_cap = "current_user_can" nocase
    condition:
        $ajax_nopriv and not $missing_cap
}

Sigma Rule

title: CVE-2025-31525 - Missing Authorization in WP Mobile Bottom Menu
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects unauthorized AJAX requests to the vulnerable plugin
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'admin-ajax.php'
        cs-uri-query|contains: 'action=mobile_menu_'
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-31525 - WP Mobile Bottom Menu Missing Authorization"; flow:to_server; content:"POST"; http_method; content:"admin-ajax.php"; http_uri; content:"action=mobile_menu_"; http_client_body; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Disable the WP Mobile Bottom Menu plugin until a patch is released.
2. Short-term: Implement a WAF rule to block requests containing action=mobile_menu_ in the POST body.
3. Long-term: Monitor the vendor's repository for updates. If no patch appears within 30 days, consider forking the plugin or migrating to an alternative.
4. Detection: Deploy the provided YARA, Sigma, and Suricata rules to detect exploitation attempts.

Valters IT
Securing Digital Frontiers