CVE-2025-39554

Executive Summary

CVE-2025-39554 is a Missing Authorization vulnerability in the AI Text to Speech WordPress plugin by Elliot Sowersby / RelyWP. This flaw allows unauthenticated attackers to exploit incorrectly configured access control security levels, potentially leading to unauthorized data access, modification, or privilege escalation. The vulnerability affects all versions up to and including 3.0.3. As of this report, no official patch has been released, and no public proof-of-concept (PoC) code is available.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin distributed via the official WordPress plugin repository. Users who have installed the plugin directly from the WordPress dashboard or via manual upload are affected. The lack of a patch increases supply chain risk, as malicious actors could exploit this flaw to compromise WordPress sites running the vulnerable plugin.

CVSS Breakdown & Threat Level

• CVSS Score: 6.5 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: Low

The vulnerability is exploitable remotely without authentication, making it a significant threat despite the medium CVSS score. The lack of a patch and the widespread use of WordPress plugins elevate the risk.

Deep Dive & Mechanics

The vulnerability stems from missing authorization checks in the plugin's AJAX handlers or REST API endpoints. The plugin likely fails to verify user capabilities (e.g., manage_options, edit_posts) before executing sensitive actions such as generating speech, modifying settings, or accessing user data. Attackers can craft HTTP requests to these unprotected endpoints to perform unauthorized operations.

Key technical details:

• The plugin registers AJAX actions for both authenticated and unauthenticated users.
• Some actions intended for administrators are not properly protected with current_user_can() checks.
• Attackers can enumerate endpoints by analyzing the plugin's JavaScript files or source code.

Vulnerable vs. Patched Code

Since no patch is available, we can only hypothesize the vulnerable code pattern:

Vulnerable Code (hypothetical):

add_action('wp_ajax_nopriv_generate_speech', 'generate_speech_callback');
function generate_speech_callback() {
    // Missing capability check
    $text = $_POST['text'];
    // Process speech generation
}

Patched Code (expected):

add_action('wp_ajax_generate_speech', 'generate_speech_callback');
function generate_speech_callback() {
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    $text = sanitize_text_field($_POST['text']);
    // Process speech generation
}

The patch would add current_user_can() checks and ensure AJAX actions are only registered for authenticated users where appropriate.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress site running AI Text to Speech <= 3.0.3
• Network access to the target

Exploitation Steps:

1. Enumerate vulnerable endpoints by inspecting the plugin's JavaScript files (e.g., /wp-content/plugins/ai-text-to-speech/assets/js/main.js).
2. Craft a POST request to an unprotected AJAX action:

curl -X POST http://target.com/wp-admin/admin-ajax.php \
  -d "action=generate_speech&text=test"

3. If successful, the response will contain generated speech data or indicate unauthorized access to protected functionality.

Note: No public exploit code is available; this is a theoretical approach.

Blue Team

Detection:

• Monitor for unusual AJAX requests to /wp-admin/admin-ajax.php with actions related to the plugin (e.g., generate_speech, save_settings).
• Look for requests from unauthenticated users to actions that should require authentication.
• Analyze server logs for 403 errors followed by successful responses to the same endpoint.

Hunting:

• Search for requests to admin-ajax.php with action parameters containing plugin-specific strings.
• Correlate with user agent anomalies or IP addresses not associated with legitimate users.

Indicators of Compromise (IOCs)

• Network:
  • POST requests to /wp-admin/admin-ajax.php with action=generate_speech or similar plugin-specific actions.
  • Unusual patterns in the text parameter (e.g., long strings, encoded payloads).
• File:
  • Modified plugin files (check file integrity via checksums).
  • Unexpected files in /wp-content/uploads/ related to speech generation.
• Log:
  • Repeated 403 errors followed by 200 responses on the same endpoint.
  • Access logs showing requests to plugin AJAX endpoints from unknown IPs.

Detection Engineering

YARA Rule

rule CVE_2025_39554_AI_Text_to_Speech {
    meta:
        description = "Detects exploitation attempts for CVE-2025-39554 in AI Text to Speech plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-39554"
    strings:
        $ajax_action = "action=generate_speech" nocase
        $plugin_path = "/wp-content/plugins/ai-text-to-speech/" nocase
        $admin_ajax = "admin-ajax.php" nocase
    condition:
        all of them
}

Sigma Rule

title: CVE-2025-39554 - AI Text to Speech Missing Authorization
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects exploitation attempts against CVE-2025-39554
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_speech'
    condition: selection
falsepositives:
    - Legitimate plugin usage by authorized users
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-39554 - AI Text to Speech Missing Authorization Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=generate_speech"; http_client_body; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released.
2. If disabling is not possible, restrict access to /wp-admin/admin-ajax.php using a Web Application Firewall (WAF) or .htaccess rules.
3. Monitor for any suspicious activity related to the plugin.

Long-term Fix:

• Apply the official patch once released by the vendor.
• Implement a WordPress security plugin that adds additional authorization checks.
• Regularly audit all installed plugins for vulnerabilities.

Workaround:

• Add the following to .htaccess to block unauthenticated AJAX requests to the plugin:

<Files "admin-ajax.php">
    Require all denied
    Require ip 127.0.0.1
</Files>

Note: This may break legitimate functionality.

Valters IT
Securing Digital Frontiers