CVE-2025-64639

Executive Summary

CVE-2025-64639 is a Missing Authorization vulnerability in the WP Compress for MainWP WordPress plugin, affecting versions up to and including 6.50.17. This flaw allows an unauthenticated attacker to exploit incorrectly configured access control security levels, potentially leading to unauthorized data access or actions within the WordPress ecosystem. The vulnerability has a CVSS score of 5.3 (Medium), with an EPSS score of 0.0%, indicating low exploitation likelihood currently. No public proof-of-concept (PoC) or patch is available at this time.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin distributed via the official WordPress plugin repository. Users are advised to monitor for updates from the vendor and apply patches immediately upon release. The lack of a patch increases supply chain risk for sites using this plugin.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
• Base Score: 5.3 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: Low (C:L)
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

Threat Level: Medium. The vulnerability is exploitable remotely without authentication, but the impact is limited to low confidentiality loss. No integrity or availability impact.

Deep Dive & Mechanics

The vulnerability stems from a Missing Authorization check (CWE-862) in the WP Compress for MainWP plugin. The plugin fails to properly verify user permissions before allowing access to certain administrative functions or data endpoints. This allows an unauthenticated attacker to send crafted HTTP requests to the WordPress site and potentially access sensitive information or perform actions that should be restricted to authenticated users with specific roles.

The flaw is specifically in the wp-compress-mainwp component, which integrates with the MainWP dashboard. The missing authorization likely occurs in REST API endpoints or AJAX handlers that do not validate the current user's capabilities before processing requests.

Vulnerable vs. Patched Code

Since no patch is available, a hypothetical fix would involve adding capability checks to all sensitive endpoints. Below is an example of vulnerable vs. patched code.

Vulnerable Code (PHP):

add_action('wp_ajax_nopriv_wp_compress_get_data', 'wp_compress_get_data');
function wp_compress_get_data() {
    // No authorization check
    $data = get_option('wp_compress_sensitive_data');
    wp_send_json_success($data);
}

Patched Code (PHP):

add_action('wp_ajax_wp_compress_get_data', 'wp_compress_get_data');
add_action('wp_ajax_nopriv_wp_compress_get_data', 'wp_compress_get_data_unauthorized');
function wp_compress_get_data() {
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    $data = get_option('wp_compress_sensitive_data');
    wp_send_json_success($data);
}
function wp_compress_get_data_unauthorized() {
    wp_die('Unauthorized', 403);
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target WordPress site with WP Compress for MainWP <= 6.50.17 installed and activated.
• No authentication required.

Exploitation Steps:

1. Identify vulnerable endpoints by analyzing the plugin's JavaScript or REST API routes.
2. Send a crafted HTTP request to the vulnerable endpoint, e.g.:

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

3. If the endpoint returns sensitive data without authentication, the vulnerability is confirmed.

Note: No public exploit code is available. The above is a generic example based on common patterns.

Blue Team

Detection Steps:

1. Monitor for unusual access to admin-ajax.php or REST API endpoints without authentication.
2. Check for requests to actions prefixed with wp_compress_ from unauthenticated users.
3. Review server logs for 403 errors followed by successful 200 responses on the same endpoint.

Hunting Query (Splunk):

index=web sourcetype=access_combined
| search uri="/wp-admin/admin-ajax.php" action=wp_compress_*
| eval authenticated=if(cookie="*wordpress_logged_in*", "yes", "no")
| where authenticated="no"
| stats count by src_ip, uri, status

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP POST requests to /wp-admin/admin-ajax.php with action=wp_compress_* parameters from unauthenticated sources.
  • Unusual outbound data transfers from the WordPress server to external IPs.

• File IOCs:

  • Modified plugin files in /wp-content/plugins/wp-compress-mainwp/ (check file integrity).
  • Suspicious log entries in /var/log/apache2/access.log or /var/log/nginx/access.log.

• Behavioral IOCs:

  • Unauthorized access to WordPress options or user meta data.
  • Unexpected changes to plugin settings.

Detection Engineering

YARA Rule

rule CVE_2025_64639_WP_Compress_Missing_Auth {
    meta:
        description = "Detects exploitation attempts for CVE-2025-64639 in WP Compress for MainWP"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-64639"
    strings:
        $ajax_action = "wp_compress_" nocase
        $admin_ajax = "admin-ajax.php" nocase
    condition:
        $ajax_action and $admin_ajax
}

Sigma Rule

title: CVE-2025-64639 - WP Compress Missing Authorization
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects unauthenticated access to WP Compress for MainWP endpoints
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-query|contains: "admin-ajax.php"
        cs-uri-query|contains: "action=wp_compress_"
        sc-status: 200
    condition: selection
falsepositives:
    - Legitimate plugin updates
level: medium

Suricata Rule

alert http any any -> $HOME_NET any (
    msg:"CVE-2025-64639 - WP Compress Missing Authorization Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"admin-ajax.php"; http_uri;
    content:"action=wp_compress_"; http_client_body;
    classtype:attempted-recon;
    sid:1000001;
    rev:1;
    reference:cve,2025-64639;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the WP Compress for MainWP plugin until a patch is available.
2. Implement a Web Application Firewall (WAF) rule to block requests to admin-ajax.php with action=wp_compress_* from unauthenticated users.
3. Monitor for any signs of exploitation using the provided detection rules.

Long-term Fix:

• Apply the official patch from the vendor once released.
• Update the plugin to the latest version.
• Conduct a security audit of all WordPress plugins for similar missing authorization issues.

Workaround:

• Add the following code to the theme's functions.php to block unauthenticated access to the vulnerable endpoints:

  add_action('init', function() {
      if (defined('DOING_AJAX') && DOING_AJAX && !is_user_logged_in()) {
          $action = $_REQUEST['action'] ?? '';
          if (strpos($action, 'wp_compress_') === 0) {
              wp_die('Unauthorized', 403);
          }
      }
  });
  

Valters IT
Securing Digital Frontiers