CVE-2025-15476

Executive Summary

CVE-2025-15476 is a Missing Authorization vulnerability in the The Bucketlister WordPress plugin, affecting all versions up to and including 0.1.5. The flaw resides in the bucketlister_do_admin_ajax() function, which fails to perform a capability check before processing AJAX requests. This allows authenticated attackers with Subscriber-level access or higher to arbitrarily add, delete, or modify bucket list items. The vulnerability has a CVSS score of 4.3 (Medium), with an EPSS probability of 0.0%, indicating low exploitation likelihood in the wild. No public exploit code or patch is currently available.

WordPress Ecosystem Context

This vulnerability is specific to the WordPress plugin ecosystem. The bucketlister_do_admin_ajax() function is intended for administrative actions but lacks proper nonce and capability verification, enabling privilege escalation from Subscriber to unauthorized data modification.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
• Base Score: 4.3 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L) – Subscriber-level
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: None (C:N)
• Integrity Impact: Low (I:L) – Unauthorized modification of bucket list items
• Availability Impact: None (A:N)

Threat Level: Medium. While the impact is limited to data integrity, the low attack complexity and minimal privileges required make it a viable target for authenticated attackers.

Deep Dive & Mechanics

The vulnerability exists in the bucketlister_do_admin_ajax() function, which is registered to handle AJAX requests for administrative bucket list operations. The function lacks a current_user_can() check or nonce verification, allowing any authenticated user (including Subscribers) to call it. The function processes actions such as adding, deleting, or modifying bucket list items via POST parameters.

Root Cause: Missing capability check (CWE-862) in the AJAX handler. The function does not verify that the user has the manage_options or edit_posts capability before executing the requested action.

Attack Flow:

1. Attacker authenticates as a Subscriber.
2. Attacker crafts a POST request to /wp-admin/admin-ajax.php with action=bucketlister_do_admin_ajax and parameters for add/delete/modify.
3. The server processes the request without authorization, modifying the bucket list data.

Vulnerable vs. Patched Code

Vulnerable Code (version <= 0.1.5):

add_action('wp_ajax_bucketlister_do_admin_ajax', 'bucketlister_do_admin_ajax');
function bucketlister_do_admin_ajax() {
    // No capability check
    $action = $_POST['bucket_action'];
    // Process action...
}

Patched Code (hypothetical):

add_action('wp_ajax_bucketlister_do_admin_ajax', 'bucketlister_do_admin_ajax');
function bucketlister_do_admin_ajax() {
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized');
    }
    check_ajax_referer('bucketlister_nonce', 'nonce');
    $action = sanitize_text_field($_POST['bucket_action']);
    // Process action...
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• WordPress instance with The Bucketlister plugin <= 0.1.5
• Valid Subscriber account credentials

Exploit Steps:

1. Log in as a Subscriber and obtain a valid WordPress nonce (if required, but the function lacks nonce check).
2. Send a crafted POST request to wp-admin/admin-ajax.php:

curl -X POST http://target.com/wp-admin/admin-ajax.php \
  -d "action=bucketlister_do_admin_ajax&bucket_action=add&item_name=malicious_item&item_value=test"

3. Verify the bucket list item was added by checking the plugin's frontend or database.

Note: No public exploit code is available; this is a conceptual demonstration.

Blue Team (Detection & Hardening)

Detection:

• Monitor AJAX requests to admin-ajax.php with action=bucketlister_do_admin_ajax from non-admin users.
• Alert on unusual bucket list modifications (e.g., high frequency, suspicious item names).

Hardening:

• Apply the principle of least privilege: ensure only administrators can access the AJAX handler.
• Implement a Web Application Firewall (WAF) rule to block requests to bucketlister_do_admin_ajax from users without manage_options capability.
• Temporarily disable the plugin until a patch is available.

Indicators of Compromise (IOCs)

• Network:
  • POST requests to /wp-admin/admin-ajax.php with action=bucketlister_do_admin_ajax
  • Parameters: bucket_action, item_name, item_value
• Logs:
  • WordPress debug log entries showing bucketlister_do_admin_ajax calls from Subscriber-level users
  • Database entries in wp_options or custom tables with unexpected bucket list items
• File System:
  • Modified plugin files (if attacker uploads malicious payloads)

Detection Engineering

YARA Rule

rule CVE_2025_15476_WordPress_Bucketlister {
    meta:
        description = "Detects exploitation attempts of CVE-2025-15476 in The Bucketlister plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-15476"
    strings:
        $ajax_handler = "bucketlister_do_admin_ajax"
        $action_param = "bucket_action"
        $item_param = "item_name"
    condition:
        all of them
}

Sigma Rule

title: CVE-2025-15476 - Bucketlister AJAX Exploitation
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects unauthorized AJAX requests to bucketlister_do_admin_ajax from non-admin users
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query: 'action=bucketlister_do_admin_ajax'
        c-uri: '/wp-admin/admin-ajax.php'
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-15476 - Bucketlister AJAX Exploitation Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=bucketlister_do_admin_ajax"; http_client_body;
    sid:1000001;
    rev:1;
    metadata:author "Valters IT", reference "CVE-2025-15476";
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patched version is released.
2. Restrict AJAX handler access by adding a capability check (see patched code example).
3. Audit user roles to ensure no Subscriber accounts have been compromised.

Long-term Fix:

• The vendor should release version 0.1.6 with proper current_user_can('manage_options') and nonce verification.
• Implement logging for all AJAX actions to detect future abuse.

Workaround:

• Use a WAF rule to block bucketlister_do_admin_ajax requests from users with role less than Administrator.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Analyst
Report generated from CVE-2025-15476 analysis