CVE-2025-62138

Executive Summary

CVE-2025-62138 is a Missing Authorization vulnerability in the WordPress plugin WP Advanced PDF (developed by Cedcommerce). This flaw allows an unauthenticated attacker to exploit incorrectly configured access control security levels, potentially leading to unauthorized access to PDF generation or retrieval functionality. The vulnerability affects all versions up to and including 1.1.7. As of this report, no official patch has been released, and no public proof-of-concept (PoC) or exploit code is available. The CVSS score of 5.3 (Medium) reflects the low complexity and network-based attack vector, but the impact is limited to confidentiality (low) with no impact on integrity or availability.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin ecosystem. The plugin is distributed via the official WordPress plugin repository and third-party marketplaces. Users are advised to monitor for updates from the vendor and consider disabling the plugin until a patch is released.

CVSS Breakdown & Threat Level

• CVSS Score: 5.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
• Attack Vector: Network (AV:N) – The vulnerability can be exploited remotely.
• Attack Complexity: Low (AC:L) – No special conditions are required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – The vulnerable component and impacted component are the same.
• Confidentiality Impact: Low (C:L) – Limited information disclosure possible.
• Integrity Impact: None (I:N) – No data modification.
• Availability Impact: None (A:N) – No denial of service.

Threat Level: Medium. The lack of authentication requirements makes this an attractive target for automated scanning and exploitation, especially in WordPress environments with the plugin installed.

Deep Dive & Mechanics

The vulnerability stems from a Missing Authorization check (CWE-862) in the WP Advanced PDF plugin. The plugin likely exposes REST API endpoints or AJAX actions that generate or serve PDF files without verifying user permissions. An attacker can directly call these endpoints to:

• Generate PDFs of private or restricted content (e.g., draft posts, private pages, or user data).
• Retrieve previously generated PDFs that should be access-controlled.
• Enumerate valid post IDs or user data through error messages or response differences.

The core issue is that the plugin fails to implement capability checks (e.g., current_user_can()) before executing sensitive operations. This is a common oversight in WordPress plugin development where developers assume that only authenticated users will access certain endpoints.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on the vulnerability type.

Vulnerable Code (wp-advanced-pdf.php or similar):

add_action('wp_ajax_nopriv_generate_pdf', 'generate_pdf_callback');
add_action('wp_ajax_generate_pdf', 'generate_pdf_callback');

function generate_pdf_callback() {
    $post_id = $_GET['post_id'];
    // No permission check!
    $post = get_post($post_id);
    // Generate PDF from post content
    // ...
}

Patched Code (Hypothetical):

add_action('wp_ajax_generate_pdf', 'generate_pdf_callback');

function generate_pdf_callback() {
    if (!current_user_can('edit_posts')) {
        wp_die('Unauthorized', 403);
    }
    $post_id = intval($_GET['post_id']);
    if (!current_user_can('read_post', $post_id)) {
        wp_die('Unauthorized', 403);
    }
    $post = get_post($post_id);
    // Generate PDF from post content
    // ...
}

The patched version removes the nopriv action (which allows unauthenticated access) and adds capability checks using current_user_can().

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A WordPress site with WP Advanced PDF <= 1.1.7 installed and activated.
• Knowledge of a valid post ID (e.g., 1, 2, etc.).

Exploitation Steps:

1. Identify the vulnerable endpoint. Common patterns include:
   • /wp-admin/admin-ajax.php?action=generate_pdf&post_id=1
   • /wp-json/wp-advanced-pdf/v1/generate/1
2. Send a direct request without authentication:

   curl -v "http://target.com/wp-admin/admin-ajax.php?action=generate_pdf&post_id=1"
   

3. If successful, the response will contain a PDF file or a link to download it.
4. Iterate through post IDs to enumerate content:

   for i in {1..100}; do
       curl -s -o "pdf_$i.pdf" "http://target.com/wp-admin/admin-ajax.php?action=generate_pdf&post_id=$i"
   done
   

Expected Outcome: Unauthorized access to PDFs of any post, including private/draft content.

Blue Team (Defensive)

Detection:

• Monitor for requests to admin-ajax.php with suspicious action parameters (e.g., generate_pdf, wp_advanced_pdf_*).
• Look for patterns of sequential post ID requests from the same IP.
• Check for 200 responses to unauthenticated requests to PDF generation endpoints.

Mitigation:

• Immediately disable the WP Advanced PDF plugin if not essential.
• Implement a Web Application Firewall (WAF) rule to block unauthenticated requests to known vulnerable endpoints.
• Use a WordPress security plugin to add virtual patching.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests to /wp-admin/admin-ajax.php with action=generate_pdf or similar.
  • Sequential post_id parameters in GET requests.
  • Unusual PDF file downloads from the server.
• File IOCs:
  • Unexpected PDF files in the server's upload or temp directories.
  • Log entries showing admin-ajax.php accessed without authentication cookies.
• Behavioral IOCs:
  • Spike in PDF generation requests from a single IP.
  • Access to private/draft posts by unauthenticated users.

Detection Engineering

YARA Rule

rule CVE_2025_62138_WP_Advanced_PDF {
    meta:
        description = "Detects exploitation attempts of CVE-2025-62138 in WP Advanced PDF plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-62138"
    strings:
        $ajax_action = "admin-ajax.php" nocase
        $pdf_action = "generate_pdf" nocase
        $post_id = "post_id=" nocase
    condition:
        all of them
}

Sigma Rule

title: CVE-2025-62138 - WP Advanced PDF Missing Authorization
id: 8a3f7c2e-5d1b-4a9f-8c6e-2b1d3f4a5c6d
status: experimental
description: Detects unauthenticated requests to WP Advanced PDF generation endpoints
author: Valters IT
date: 2025/04/10
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-uri-query|contains:
            - "admin-ajax.php?action=generate_pdf"
            - "wp-advanced-pdf/v1/generate"
        sc-status: 200
    condition: selection
falsepositives:
    - Legitimate admin users (should be authenticated)
level: medium

Suricata Rule

alert http any any -> $HOME_NET any (
    msg:"CVE-2025-62138 - WP Advanced PDF Missing Authorization Exploit Attempt";
    flow:to_server,established;
    content:"GET"; http_method;
    content:"admin-ajax.php"; http_uri;
    content:"action=generate_pdf"; http_uri;
    content:"post_id="; http_uri;
    classtype:attempted-recon;
    sid:10000001;
    rev:1;
    reference:cve,2025-62138;
    priority:2;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin – Deactivate and uninstall WP Advanced PDF until a patch is released.
2. Virtual Patching – Use a WAF to block unauthenticated requests to admin-ajax.php with action=generate_pdf or similar patterns.
3. Monitor Logs – Review web server access logs for exploitation attempts.

Long-term Fix:

• The vendor (Cedcommerce) must release a patched version that implements proper capability checks using current_user_can() or wp_verify_nonce().
• Users should update to the latest version once available.

Workaround:

• If the plugin is critical, restrict access to the vulnerable endpoints via .htaccess:

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

  (Note: This will break legitimate AJAX functionality for all plugins.)

Valters IT
Securing Digital Frontiers