CVE-2025-31856

Executive Summary

CVE-2025-31856 is a Missing Authorization vulnerability in the Export All Post Meta WordPress plugin by Brainvireinfo, affecting versions from n/a through 1.2.1. This flaw allows unauthenticated attackers to access functionality that should be constrained by Access Control Lists (ACLs), specifically the export of all post meta data. The vulnerability has a CVSS score of 4.3 (Medium) and an EPSS score of 0.0%, indicating low exploitation likelihood at this time. No public proof-of-concept or patch details are currently available.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed through the official WordPress plugin repository. As a WordPress ecosystem issue, it impacts site owners who have installed the plugin. The lack of a patch or advisory from the vendor increases supply chain risk, as users must rely on manual mitigation or removal of the plugin.

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) – Impact confined to the vulnerable component.
• Confidentiality (C): Low (L) – Limited exposure of post meta data.
• Integrity (I): None (N) – No data modification.
• Availability (A): None (N) – No denial of service.

Threat Level: Medium. The vulnerability allows unauthorized access to potentially sensitive post metadata, but does not enable data modification or system compromise.

Deep Dive & Mechanics

The vulnerability resides in the export-all-post-meta plugin, which provides functionality to export all post meta data (custom fields) from a WordPress site. The plugin fails to properly enforce authorization checks on its AJAX handlers or direct endpoints, allowing any unauthenticated user to trigger the export process.

Root Cause: The plugin registers AJAX actions (e.g., wp_ajax_export_all_post_meta and wp_ajax_nopriv_export_all_post_meta) without verifying user capabilities. The nopriv hook indicates the action is accessible to unauthenticated users, but the plugin does not include a current_user_can() check or nonce verification before executing the export.

Attack Vector: An attacker can craft a simple HTTP request to the WordPress admin-ajax.php endpoint with the appropriate action parameter to trigger the export. The exported data includes all post meta fields, which may contain sensitive information such as API keys, user session tokens, or internal configuration data.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to be in the plugin's main PHP file (e.g., export-all-post-meta.php). The vulnerable pattern is:

// Vulnerable: No capability check
add_action('wp_ajax_export_all_post_meta', 'export_all_post_meta_callback');
add_action('wp_ajax_nopriv_export_all_post_meta', 'export_all_post_meta_callback');

function export_all_post_meta_callback() {
    // Export logic without checking user permissions
    $posts = get_posts(array('numberposts' => -1));
    foreach ($posts as $post) {
        $meta = get_post_meta($post->ID);
        // Output or save meta data
    }
    wp_die();
}

A patched version would include:

// Patched: Add capability check
add_action('wp_ajax_export_all_post_meta', 'export_all_post_meta_callback');
// Remove nopriv action to block unauthenticated access

function export_all_post_meta_callback() {
    // Verify user has proper capability
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    // Verify nonce
    check_ajax_referer('export_all_post_meta_nonce', 'nonce');
    
    // Export logic
    $posts = get_posts(array('numberposts' => -1));
    foreach ($posts as $post) {
        $meta = get_post_meta($post->ID);
        // Output or save meta data
    }
    wp_die();
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Target WordPress site with Export All Post Meta plugin <= 1.2.1 installed and activated.
• No authentication required.

Exploitation Steps:

1. Identify Target: Use Shodan dorks or manual reconnaissance to find vulnerable sites.

2. Craft Request: Send a POST request to the WordPress admin-ajax.php endpoint:

curl -X POST https://target.com/wp-admin/admin-ajax.php \
  -d "action=export_all_post_meta"

3. Retrieve Data: The response will contain all post meta data in CSV or JSON format, depending on the plugin's implementation.

Expected Output: A file containing post IDs, meta keys, and meta values for all posts on the site.

Blue Team (Detection & Defense)

Detection:

• Monitor for unusual requests to /wp-admin/admin-ajax.php with the action=export_all_post_meta parameter.
• Alert on high volume of post meta retrieval from unauthenticated sources.

Defense:

• Immediately disable or remove the plugin if no patch is available.
• Implement Web Application Firewall (WAF) rules to block requests to admin-ajax.php with the export_all_post_meta action from unauthenticated users.
• Restrict access to admin-ajax.php using IP whitelisting or .htaccess rules.

Indicators of Compromise (IOCs)

• Network:

  • HTTP POST requests to /wp-admin/admin-ajax.php with body containing action=export_all_post_meta
  • Unusual outbound data transfers from the WordPress server containing post meta data

• File System:

  • Presence of unexpected CSV or JSON files in the web root or uploads directory containing post meta data

• Logs:

  • WordPress debug log entries showing export_all_post_meta_callback function calls
  • Web server access logs showing repeated requests to admin-ajax.php with the export_all_post_meta parameter

Detection Engineering

YARA Rule

rule Detect_Export_All_Post_Meta_Exploit {
    meta:
        description = "Detects exploitation attempts of CVE-2025-31856"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-31856"
    strings:
        $action = "action=export_all_post_meta"
        $ajax = "admin-ajax.php"
    condition:
        $action and $ajax
}

Sigma Rule

title: CVE-2025-31856 - Export All Post Meta Exploitation
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects exploitation attempts of the Missing Authorization vulnerability in Export All Post Meta plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'admin-ajax.php'
        cs-uri-query|contains: 'action=export_all_post_meta'
    condition: selection
falsepositives:
    - Legitimate admin usage (if plugin is used by authorized users)
level: high

Suricata Rule

alert http any any -> $EXTERNAL_NET any (
    msg:"CVE-2025-31856 - Export All Post Meta Exploitation Attempt";
    flow:to_server,established;
    content:"POST";
    http_method;
    content:"admin-ajax.php";
    http_uri;
    content:"action=export_all_post_meta";
    http_client_body;
    classtype:attempted-recon;
    sid:10000001;
    rev:1;
    reference:cve,2025-31856;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin: Deactivate and delete the Export All Post Meta plugin from all WordPress installations.
2. Audit for exposure: Check web server logs for any unauthorized access to admin-ajax.php with the export_all_post_meta action.
3. Rotate secrets: If sensitive data (API keys, tokens) was exposed, rotate them immediately.

Long-term Mitigation:

• Monitor the WordPress plugin repository for an official patch.
• Implement a Web Application Firewall (WAF) with rules to block unauthenticated access to AJAX actions.
• Apply the principle of least privilege to all WordPress plugins and users.
• Regularly audit installed plugins for known vulnerabilities.

Workaround (if plugin must remain active):

• Add a custom capability check via a mu-plugin:

add_action('wp_ajax_export_all_post_meta', function() {
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
}, 1);

Valters IT
Securing Digital Frontiers