CVE-2025-62883

Executive Summary

CVE-2025-62883 is a Missing Authorization vulnerability in the Premmerce User Roles WordPress plugin (versions <= 1.0.13). This flaw allows an unauthenticated attacker to exploit incorrectly configured access control security levels, potentially leading to unauthorized access to sensitive user role data or privilege escalation. The vulnerability resides in the WordPress ecosystem and is not related to Apache or Nginx.

The CVSS score is 4.3 (Medium), with a low EPSS probability (0.0%), indicating limited active exploitation at this time. However, due to the lack of a vendor patch, this vulnerability poses a persistent risk to WordPress sites using the plugin.

Supply Chain & Package Security

This is a WordPress plugin vulnerability. No NPM, PyPI, Go, or Ruby packages are involved. The plugin is distributed via the WordPress plugin repository and third-party marketplaces. Users should verify the integrity of their plugin files and monitor for unauthorized modifications.

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 information disclosure.
• Integrity (I): None (N) – No data modification.
• Availability (A): None (N) – No denial of service.

Threat Level: Medium – Exploitation is straightforward but impact is limited to unauthorized access to user role configurations.

Deep Dive & Mechanics

The vulnerability stems from missing authorization checks in the premmerce-user-roles plugin. The plugin likely exposes REST API endpoints or AJAX actions that modify or retrieve user role settings without verifying the user’s capabilities. An unauthenticated attacker can send crafted HTTP requests to these endpoints to:

• List all user roles and their capabilities.
• Modify role permissions (e.g., grant administrator privileges).
• Create or delete custom roles.

The core issue is the absence of current_user_can() checks or nonce verification in the plugin’s backend handlers. This allows any remote user to invoke privileged functions.

Vulnerable vs. Patched Code

Vulnerable Code (<= 1.0.13):

// Example of missing authorization in an AJAX handler
add_action('wp_ajax_premmerce_update_role', 'premmerce_update_role_callback');
add_action('wp_ajax_nopriv_premmerce_update_role', 'premmerce_update_role_callback'); // No privilege check

function premmerce_update_role_callback() {
    $role = sanitize_text_field($_POST['role']);
    $capability = sanitize_text_field($_POST['capability']);
    // Directly modifies role without checking user capabilities
    $wp_roles->add_cap($role, $capability);
    wp_die();
}

Patched Code (Hypothetical):

add_action('wp_ajax_premmerce_update_role', 'premmerce_update_role_callback');
// Remove nopriv action to require authentication
function premmerce_update_role_callback() {
    // Add capability check
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    // Verify nonce
    if (!wp_verify_nonce($_POST['_wpnonce'], 'premmerce_update_role')) {
        wp_die('Nonce verification failed', 403);
    }
    $role = sanitize_text_field($_POST['role']);
    $capability = sanitize_text_field($_POST['capability']);
    $wp_roles->add_cap($role, $capability);
    wp_die();
}

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• Target WordPress site with Premmerce User Roles <= 1.0.13 installed.
• Network access to the site.

Exploitation Steps:

1. Enumerate vulnerable endpoints (e.g., /wp-admin/admin-ajax.php).
2. Craft a POST request to add a new administrator role or grant admin capabilities to an existing user.

Example Exploit (cURL):

# Grant 'administrator' capabilities to the 'subscriber' role
curl -X POST https://target.com/wp-admin/admin-ajax.php \
  -d "action=premmerce_update_role&role=subscriber&capability=administrator"

Expected Outcome: The subscriber role gains administrator-level capabilities, allowing privilege escalation.

Blue Team (Defender)

Detection & Response:

• Monitor for unusual AJAX requests to admin-ajax.php with action=premmerce_* parameters.
• Alert on any role modification events without proper authentication.
• Use Web Application Firewall (WAF) rules to block unauthenticated requests to plugin-specific actions.

Hunting Query (Splunk):

index=web sourcetype=access_combined
| search uri="/wp-admin/admin-ajax.php" AND form_data=*premmerce_*
| eval auth=if(mvindex(form_data, match(form_data, "action=premmerce_")) != "", "unauthenticated", "authenticated")
| where auth="unauthenticated"
| table _time, src_ip, uri, form_data

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP POST requests to /wp-admin/admin-ajax.php with action=premmerce_* parameters.
  • Unusual user role changes in WordPress logs (e.g., wp_user_roles option modifications).
• File IOCs:
  • Modified plugin files in /wp-content/plugins/premmerce-user-roles/.
  • Suspicious PHP files uploaded to the uploads directory.
• Log IOCs:
  • WordPress debug log entries showing wp_ajax_nopriv_premmerce_* actions.
  • Apache/Nginx access logs with POST /wp-admin/admin-ajax.php from unknown IPs.

Detection Engineering

YARA Rule

rule premmerce_user_roles_missing_auth {
    meta:
        description = "Detects missing authorization in Premmerce User Roles plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-62883"
    strings:
        $ajax_handler = /add_action\s*\(\s*['\"]wp_ajax_nopriv_premmerce_/
        $no_cap_check = /current_user_can\s*\(/
    condition:
        $ajax_handler and not $no_cap_check
}

Sigma Rule

title: Premmerce User Roles Missing Authorization Exploitation
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects exploitation attempts of CVE-2025-62883 via unauthenticated AJAX requests
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: POST
        cs-uri-stem: /wp-admin/admin-ajax.php
        cs-uri-query|contains: action=premmerce_
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: high

Suricata Rule

alert http any any -> $EXTERNAL_NET any (
    msg:"CVE-2025-62883 Premmerce User Roles Missing Authorization Exploit";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=premmerce_"; http_client_body;
    classtype:attempted-admin;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is available.
2. Implement a Web Application Firewall (WAF) rule to block unauthenticated requests to admin-ajax.php with action=premmerce_*.
3. Review user roles for unauthorized modifications and revert any changes.

Long-Term Fixes:

• Vendor Patch: Await an official update from Premmerce that adds proper capability checks and nonce verification.
• Custom Hardening: Add the following code to the theme's functions.php to block unauthenticated AJAX actions:

add_action('wp_ajax_nopriv_premmerce_update_role', function() {
    wp_die('Unauthorized', 403);
}, 1);

• Monitor Plugin Updates: Subscribe to WordPress security advisories for Premmerce plugins.

Valters IT – Securing WordPress ecosystems one CVE at a time.