CVE-2025-49289

Executive Summary

CVE-2025-49289 is a Missing Authorization vulnerability in the WordPress plugin PDF for WPForms by add-ons.org. This flaw allows an unauthenticated attacker to exploit incorrectly configured access control security levels, potentially leading to unauthorized access to PDF generation functionality. The vulnerability affects all versions up to and including 5.5.0. With a CVSS score of 5.0 (Medium), the primary risk is the exposure of sensitive data through improperly secured PDF generation endpoints. No public exploit code or patch is currently available, but the vulnerability is considered exploitable due to the lack of required authentication checks.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin ecosystem. The plugin is distributed via the WordPress plugin repository and third-party marketplaces. Users are advised to verify the integrity of their plugin files and monitor for updates from the vendor. Since no patch is available, organizations should consider disabling the plugin or implementing virtual patching via a Web Application Firewall (WAF).

CVSS Breakdown & Threat Level

• CVSS Score: 5.0 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: Low
• Integrity Impact: None
• Availability Impact: None

The low complexity and lack of authentication requirements make this vulnerability easily exploitable. The primary threat is unauthorized access to PDF generation, which could expose sensitive form data.

Deep Dive & Mechanics

The vulnerability lies in the pdf-for-wpforms plugin's failure to properly enforce authorization checks on its AJAX handlers or REST endpoints responsible for generating PDFs. In WordPress, plugins often register AJAX actions for both authenticated and unauthenticated users. If the developer incorrectly sets the action hook (e.g., using wp_ajax_nopriv_* without proper capability checks), an attacker can trigger PDF generation without any authentication.

The plugin likely exposes a function like generate_pdf() that is hooked to wp_ajax_nopriv_pdf_for_wpforms_generate. This function should check for a valid nonce and user capabilities, but due to the missing authorization, it processes the request regardless. An attacker can craft a simple HTTP request to the WordPress admin-ajax.php endpoint with the appropriate action parameter to generate PDFs containing form submissions.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to be:

// Vulnerable code in pdf-for-wpforms.php
add_action('wp_ajax_nopriv_pdf_for_wpforms_generate', 'pdf_for_wpforms_generate_pdf');
function pdf_for_wpforms_generate_pdf() {
    // Missing capability check and nonce verification
    $form_id = $_POST['form_id'];
    // Generate PDF without verifying user permissions
    // ...
}

A patched version would include:

// Patched code
add_action('wp_ajax_pdf_for_wpforms_generate', 'pdf_for_wpforms_generate_pdf');
function pdf_for_wpforms_generate_pdf() {
    // Verify nonce
    if (!wp_verify_nonce($_POST['_wpnonce'], 'pdf_for_wpforms_nonce')) {
        wp_die('Security check failed');
    }
    // Check user capability
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized');
    }
    $form_id = intval($_POST['form_id']);
    // Generate PDF
    // ...
}

Exploitation & Lab Setup

Red Team

1. Setup: Deploy a WordPress instance with PDF for WPForms <= 5.5.0 installed and activated. Create a form with some test submissions.
2. Exploit: Send a crafted POST request to http://target/wp-admin/admin-ajax.php with the following parameters:
   • action=pdf_for_wpforms_generate
   • form_id=1 (or any valid form ID)
   • Optionally, add _wpnonce if required (but the vulnerability implies it's not checked).
3. Verification: The server will return a PDF file containing the form data without requiring authentication.

curl -X POST http://target/wp-admin/admin-ajax.php \
  -d "action=pdf_for_wpforms_generate&form_id=1" \
  -o exploit.pdf

Blue Team

1. Detection: Monitor for unusual requests to /wp-admin/admin-ajax.php with the action parameter containing pdf_for_wpforms_generate from unauthenticated sources.
2. Mitigation: Implement a WAF rule to block requests to admin-ajax.php with action=pdf_for_wpforms_generate unless they include a valid nonce.
3. Harden: Disable the plugin until a patch is available. Alternatively, remove the vulnerable AJAX hook by adding the following to a custom plugin or theme's functions.php:

remove_action('wp_ajax_nopriv_pdf_for_wpforms_generate', 'pdf_for_wpforms_generate_pdf');

Indicators of Compromise (IOCs)

• Network: HTTP POST requests to /wp-admin/admin-ajax.php with action=pdf_for_wpforms_generate and no valid _wpnonce parameter.
• File: Unexpected PDF files generated in the server's temporary directory or /wp-content/uploads/ with names like form-1-*.pdf.
• Log: WordPress debug log entries showing PHP Notice: Undefined index: _wpnonce in pdf-for-wpforms.php.
• Process: Unusual PHP processes executing wp_remote_post or file_get_contents to generate PDFs.

Detection Engineering

YARA Rule

rule CVE_2025_49289_PDF_for_WPForms {
    meta:
        description = "Detects exploitation attempts for CVE-2025-49289 in PDF for WPForms plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-49289"
    strings:
        $s1 = "pdf_for_wpforms_generate" ascii wide nocase
        $s2 = "admin-ajax.php" ascii wide nocase
        $s3 = "form_id=" ascii wide nocase
    condition:
        all of them
}

Sigma Rule

title: CVE-2025-49289 - Missing Authorization in PDF for WPForms
id: 8a4b3c2d-1e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects unauthenticated requests to the PDF generation endpoint in PDF for WPForms plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'action=pdf_for_wpforms_generate'
        c-uri|contains: '/wp-admin/admin-ajax.php'
    condition: selection
falsepositives:
    - Legitimate admin users with valid nonces (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-49289 - PDF for WPForms Missing Authorization Exploit"; flow:to_server,established; http.method; content:"POST"; http.uri; content:"/wp-admin/admin-ajax.php"; http.client_body; content:"action=pdf_for_wpforms_generate"; nocase; classtype:attempted-recon; sid:10000001; rev:1;)

Remediation & Mitigation

1. Immediate: Disable the PDF for WPForms plugin until a patch is released.
2. Virtual Patching: Add a WAF rule to block requests to /wp-admin/admin-ajax.php with action=pdf_for_wpforms_generate from unauthenticated users.
3. Code Fix: If you have developer access, modify the plugin to require authentication and nonce verification as shown in the patched code example.
4. Monitoring: Enable detailed logging for AJAX requests and monitor for suspicious activity.
5. Update: Watch the WordPress plugin repository for an official update and apply it immediately when available.

Valters IT
Securing Digital Frontiers