CVE-2025-26764

Executive Summary

CVE-2025-26764 is a Missing Authorization vulnerability in the Distance Based Shipping Calculator WordPress plugin by enituretechnology. This flaw allows unauthenticated attackers to exploit incorrectly configured access control security levels, potentially leading to unauthorized data access or manipulation of shipping calculations. The vulnerability affects all versions up to and including 2.0.22. With a CVSS score of 6.5 (Medium), it poses a significant risk to e-commerce sites relying on this plugin for shipping logic. No public proof-of-concept or patch is currently available, making proactive detection and mitigation critical.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin distributed via the official WordPress plugin repository. Organizations using this plugin should verify its integrity by checking checksums against the repository and monitoring for unauthorized modifications. Since the plugin handles shipping cost calculations, exploitation could lead to financial fraud or data exfiltration.

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 data exposure.
• Integrity (I): Low (L) – Limited data modification.
• Availability (A): None (N) – No denial-of-service impact.

Threat Level: Medium. The low complexity and lack of authentication make this an attractive target for automated scanning and exploitation.

Deep Dive & Mechanics

The vulnerability stems from missing authorization checks in AJAX handlers or REST API endpoints within the Distance Based Shipping Calculator plugin. WordPress plugins often expose admin-ajax.php or REST routes for frontend functionality. When these endpoints fail to verify user capabilities (e.g., manage_options or edit_posts), unauthenticated attackers can invoke them.

Attack Flow:

1. Attacker identifies the vulnerable endpoint (e.g., /wp-admin/admin-ajax.php?action=dbsc_update_settings).
2. Sends a crafted POST request with malicious parameters.
3. The plugin processes the request without checking if the user is an administrator.
4. Attacker modifies shipping rates, accesses customer data, or disables the plugin.

Root Cause: The plugin uses wp_ajax_ hooks but omits wp_ajax_nopriv_ checks or fails to call current_user_can() before processing sensitive actions.

Vulnerable vs. Patched Code

Vulnerable Code (<= 2.0.22):

add_action('wp_ajax_dbsc_update_settings', 'dbsc_update_settings_callback');
function dbsc_update_settings_callback() {
    // Missing capability check
    update_option('dbsc_shipping_rates', $_POST['rates']);
    wp_die();
}

Patched Code (Hypothetical):

add_action('wp_ajax_dbsc_update_settings', 'dbsc_update_settings_callback');
function dbsc_update_settings_callback() {
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    check_admin_referer('dbsc_update_settings_nonce');
    update_option('dbsc_shipping_rates', sanitize_text_field($_POST['rates']));
    wp_die();
}

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Install WordPress 6.x with Distance Based Shipping Calculator <= 2.0.22.
2. Identify AJAX actions via plugin source code or by monitoring network traffic.

Exploitation Steps:

1. Enumerate AJAX actions:

   curl -s http://target/wp-admin/admin-ajax.php?action=dbsc_get_settings
   

2. Exploit missing authorization to modify settings:

   curl -X POST http://target/wp-admin/admin-ajax.php \
     -d "action=dbsc_update_settings&rates={\"free\":\"0\"}"
   

3. Verify changes by checking shipping rates on the frontend.

Blue Team (Defensive)

Detection:

• Monitor for unusual AJAX requests to admin-ajax.php with unknown actions.
• Alert on POST requests to /wp-admin/admin-ajax.php from unauthenticated users.
• Check for rapid changes to wp_options table entries related to dbsc_.

Hunting:

• Search logs for action=dbsc_ parameters.
• Review WordPress user capability logs for unauthorized manage_options attempts.

Indicators of Compromise (IOCs)

• Network:
  • POST requests to /wp-admin/admin-ajax.php with action=dbsc_* parameters.
  • Unusual User-Agent strings in AJAX requests.
• File System:
  • Modified wp_options entries: dbsc_shipping_rates, dbsc_api_key.
  • Unexpected files in /wp-content/plugins/distance-based-shipping-calculator/.
• Logs:
  • WordPress debug log entries: PHP Notice: Undefined index: rates in ....
  • Web server logs with 200 responses to admin-ajax.php from non-admin IPs.

Detection Engineering

YARA Rule

rule CVE_2025_26764_WordPress_Plugin {
    meta:
        description = "Detects vulnerable Distance Based Shipping Calculator plugin files"
        author = "Valters IT"
        date = "2025-04-01"
        hash = "sha256:target_file_hash"
    strings:
        $vuln_func = "add_action('wp_ajax_dbsc_" ascii wide nocase
        $missing_check = "current_user_can" ascii wide nocase
    condition:
        $vuln_func and not $missing_check
}

Sigma Rule

title: CVE-2025-26764 - Missing Authorization in Distance Based Shipping Calculator
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects exploitation attempts against missing authorization in the plugin
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'admin-ajax.php'
        cs-uri-query|contains|all:
            - 'action=dbsc_'
            - 'rates='
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: high

Suricata Rule

alert http $EXTERNAL_NET any -> $HOME_NET any (
    msg:"CVE-2025-26764 - Missing Authorization in Distance Based Shipping Calculator";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"admin-ajax.php"; http_uri;
    content:"action=dbsc_"; http_client_body;
    content:"rates="; http_client_body;
    classtype:attempted-admin;
    sid:10000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin if not critical for business operations.
2. Apply virtual patching via WAF rules blocking action=dbsc_* requests from unauthenticated users.
3. Monitor logs for exploitation attempts.

Long-Term Fix:

• Update to a patched version once released by the vendor.
• Implement a Web Application Firewall (WAF) rule to block unauthorized AJAX requests.
• Conduct a security audit of all WordPress plugins for similar authorization flaws.

Workaround:

• Add the following code to the theme's functions.php to block unauthenticated AJAX calls:

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

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert