CVE-2025-62091

Executive Summary

CVE-2025-62091 is a Missing Authorization vulnerability in the Vollstart Serial Codes Generator and Validator with WooCommerce Support plugin for WordPress. This flaw allows an authenticated attacker (with low privileges) to exploit incorrectly configured access control security levels, potentially leading to unauthorized access to serial code generation and validation functionalities. The vulnerability affects all versions up to and including 2.8.2. As of this report, no official patch has been released, and no public proof-of-concept (PoC) or exploit code is available. The EPSS score is 0.0%, indicating a very low probability of exploitation in the wild at this time.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin distributed via the official WordPress plugin repository. Users who have installed this plugin from the repository are affected. There is no known compromise of the plugin’s supply chain, but the lack of a patch means that users must rely on manual mitigation or removal of the plugin.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
• Base Score: 5.4 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L) – attacker must have a valid WordPress user account (e.g., subscriber).
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: Low (C:L) – potential exposure of serial codes or configuration data.
• Integrity Impact: Low (I:L) – possible unauthorized modification of serial codes or settings.
• Availability Impact: None (A:N)

Threat Level: Medium. The vulnerability requires authentication, but low-privilege accounts (e.g., subscribers) are sufficient. Exploitation could lead to unauthorized access to serial code generation and validation, which may be used for fraud or bypassing licensing controls.

Deep Dive & Mechanics

The vulnerability stems from Missing Authorization (CWE-862) in the plugin’s AJAX handlers or REST API endpoints. The plugin likely implements custom AJAX actions or WordPress REST API routes for generating and validating serial codes. These endpoints are intended to be restricted to administrators or shop managers, but due to improper capability checks, any authenticated user can invoke them.

Root Cause: The plugin fails to call current_user_can() or wp_verify_nonce() on critical functions, allowing low-privilege users to:

• Generate new serial codes.
• Validate existing serial codes.
• Access or modify serial code settings.

Attack Scenario:

1. An attacker registers a subscriber account on a WordPress site using this plugin.
2. The attacker identifies the vulnerable AJAX action (e.g., wp_ajax_generate_serial_code).
3. The attacker sends a crafted POST request with the required parameters.
4. The server processes the request without checking user capabilities, generating a valid serial code.
5. The attacker can then use this code for unauthorized product activation or resell it.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on common fixes for CWE-862.

Vulnerable Code (example):

add_action('wp_ajax_generate_serial_code', 'generate_serial_code_callback');

function generate_serial_code_callback() {
    // No capability check
    $code = generate_new_code();
    echo json_encode(array('success' => true, 'code' => $code));
    wp_die();
}

Patched Code (example):

add_action('wp_ajax_generate_serial_code', 'generate_serial_code_callback');

function generate_serial_code_callback() {
    // Check if user has 'manage_options' capability
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    $code = generate_new_code();
    echo json_encode(array('success' => true, 'code' => $code));
    wp_die();
}

The patched version adds a capability check (current_user_can('manage_options')) to ensure only administrators can generate serial codes.

Exploitation & Lab Setup

Red Team (Proof of Concept)

Prerequisites:

• A WordPress site with the vulnerable plugin installed (version <= 2.8.2).
• A valid low-privilege user account (e.g., subscriber).

Steps:

1. Log in as the low-privilege user and obtain a WordPress nonce (if required) or session cookie.
2. Identify the vulnerable AJAX action. Common actions include:
   • wp_ajax_generate_serial_code
   • wp_ajax_validate_serial_code
3. Send a crafted request using curl:

curl -X POST \
  -c /tmp/cookies.txt -b /tmp/cookies.txt \
  -d "action=generate_serial_code&nonce=YOUR_NONCE" \
  http://target.com/wp-admin/admin-ajax.php

If successful, the response will contain a new serial code.

Note: No public exploit code is available. The above is a generic example.

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual AJAX requests from low-privilege users to admin-ajax.php with actions related to serial codes.
• Look for rapid generation of serial codes from non-admin accounts.

Hardening:

• Immediate: Disable or remove the plugin until a patch is released.
• Workaround: Use a Web Application Firewall (WAF) to block requests to admin-ajax.php from non-admin users for specific actions.
• Code Fix: Add capability checks as shown in the patched code example.

Indicators of Compromise (IOCs)

• Network IOCs:
  • POST requests to /wp-admin/admin-ajax.php with action=generate_serial_code or action=validate_serial_code from non-admin IPs.
  • Unusual volume of serial code generation requests.
• File IOCs:
  • Modified plugin files (e.g., serial-codes-generator-and-validator.php) with added malicious code.
• Log IOCs:
  • WordPress debug logs showing failed capability checks (if logging is enabled).
  • WooCommerce order logs with serial codes generated outside normal purchase flow.

Detection Engineering

YARA Rule

rule Detect_Vollstart_Serial_Codes_Missing_Auth {
    meta:
        description = "Detects vulnerable versions of Vollstart Serial Codes Generator plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-62091"
    strings:
        $vuln_func = "generate_serial_code_callback" nocase
        $missing_check = "current_user_can" nocase
    condition:
        $vuln_func and not $missing_check
}

Sigma Rule

title: Suspicious AJAX Request to Serial Codes Generator
id: 8f7a3b2c-1d4e-5f6a-7b8c-9d0e1f2a3b4c
status: experimental
description: Detects low-privilege users accessing serial code generation AJAX endpoints
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=generate_serial_code'
    condition: selection
falsepositives:
    - Legitimate admin actions (if admin uses same endpoint)
level: medium

Suricata Rule

alert http any any -> $HOME_NET any (
    msg:"CVE-2025-62091 - Vollstart Serial Codes Generator Missing Auth Attempt";
    flow:to_server,established;
    content:"POST";
    http_method;
    content:"/wp-admin/admin-ajax.php";
    http_uri;
    content:"action=generate_serial_code";
    http_client_body;
    classtype:attempted-admin;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released by the vendor.
2. Review user accounts for any unauthorized serial code generation.
3. Implement a WAF rule to block AJAX requests to admin-ajax.php with action=generate_serial_code from non-admin IPs.

Long-term Fix:

• Apply the vendor’s patch when available.
• If the plugin is abandoned, consider replacing it with an alternative that has proper access controls.

Workaround Code (if plugin must remain active): Add the following to your theme’s functions.php to enforce capability checks:

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

Note: This workaround may break if the plugin uses different action names.

Valters IT