CVE-2025-6786

Executive Summary

CVE-2025-6786 is a vulnerability in the DocCheck Login WordPress plugin (versions up to and including 1.1.5) that allows unauthenticated attackers to bypass access controls on password-protected posts. The plugin improperly redirects users to a login page after the protected post content has already been loaded in the browser, enabling attackers to read restricted content without authentication. This is a WordPress ecosystem issue, not related to the underlying web server (Apache/Nginx).

The vulnerability has a CVSS score of 5.3 (Medium) and an EPSS score of 0.0%, indicating low exploitation likelihood in the wild. No public exploit code or Nuclei template is available, but the attack vector is straightforward and requires no special privileges.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users should verify the integrity of their plugin files and monitor for updates. No known supply chain compromise has been reported.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
• Base Score: 5.3 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: Low (C:L)
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

The threat is limited to unauthorized reading of password-protected posts. No data modification or denial of service is possible.

Deep Dive & Mechanics

The vulnerability stems from the plugin's handling of password-protected posts. When an unauthenticated user requests such a post, the plugin loads the full post content into the DOM and then redirects the user to the login page. However, the content remains accessible in the page source or via JavaScript before the redirect completes.

Root Cause: The plugin does not check user authentication status before rendering the post content. It relies on a client-side redirect after the content is already sent to the browser.

Attack Vector: An unauthenticated attacker can:

1. Send a request to a password-protected post URL.
2. Intercept the response before the redirect (e.g., using curl with -L disabled or a browser's developer tools).
3. Read the post content from the response body.

Proof of Concept (Conceptual):

curl -k -L --max-redirs 0 "https://target.com/password-protected-post/"

The response will contain the post content in the HTML body before the redirect header.

Vulnerable vs. Patched Code

Vulnerable Code (DocCheck Login <= 1.1.5): The plugin likely uses a filter like the_content or template_redirect to display the post content before checking authentication. Example vulnerable pattern:

add_action('template_redirect', function() {
    // No authentication check before loading content
    $post = get_post();
    if (post_password_required($post)) {
        // Content is already loaded, then redirect
        wp_redirect(wp_login_url(get_permalink($post)));
        exit;
    }
});

Patched Code (Hypothetical): The fix should check authentication before loading the post content:

add_action('template_redirect', function() {
    if (!is_user_logged_in() && post_password_required()) {
        auth_redirect();
    }
    // Load content only after authentication
});

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Install WordPress with DocCheck Login plugin version 1.1.5.
2. Create a password-protected post with sensitive content.
3. Access the post URL without authentication.

Exploitation Steps:

1. Use curl to fetch the post without following redirects:

   curl -v --max-redirs 0 "http://target/wp/password-protected-post/"
   

2. Parse the response body for the post content (visible before the redirect header).
3. Alternatively, use a browser with network tab open to capture the initial response.

Automated Script (Python):

import requests

url = "http://target/wp/password-protected-post/"
response = requests.get(url, allow_redirects=False)
if response.status_code == 200:
    print("Post content:", response.text)

Blue Team

Detection:

• Monitor for requests to password-protected posts without subsequent login attempts.
• Look for HTTP 200 responses on protected post URLs followed by 302 redirects.
• Analyze server logs for patterns: GET /password-protected-post/ returning 200 instead of 302.

Hunting Query (Splunk):

index=web sourcetype=access_combined
| search uri="/password-protected-post/"
| eval status_code=status
| where status_code=200
| table _time, clientip, uri, status_code

Indicators of Compromise (IOCs)

• Network:
  • HTTP requests to password-protected post URLs returning 200 status.
  • Response bodies containing post content before redirect headers.
• File:
  • Plugin file: /wp-content/plugins/doccheck-login/doccheck-login.php (version 1.1.5 or lower).
• Log:
  • Web server logs showing 200 for protected post URIs.

Detection Engineering

YARA Rule

rule CVE_2025_6786_DocCheck_Login
{
    meta:
        description = "Detects DocCheck Login plugin vulnerable to CVE-2025-6786"
        author = "Valters IT"
        date = "2025-04-01"
        reference = "CVE-2025-6786"
    strings:
        $plugin_header = "Plugin Name: DocCheck Login"
        $version_string = "Version: 1.1.5"
        $vuln_pattern = "post_password_required" nocase
    condition:
        $plugin_header and ($version_string or $vuln_pattern)
}

Sigma Rule

title: CVE-2025-6786 - Unauthorized Post Access via DocCheck Login
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP 200 responses to password-protected posts indicating potential exploitation
author: Valters IT
date: 2025-04-01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-query|contains: "/password-protected-post/"
        sc-status: 200
    condition: selection
falsepositives:
    - Legitimate authenticated access (unlikely for password-protected posts)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-6786 - DocCheck Login Unauthorized Post Access"; flow:to_server,established; content:"GET"; http_method; content:"/password-protected-post/"; http_uri; pcre:"/^HTTP\/1\.[01] 200/"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the DocCheck Login plugin until a patch is available.
2. Implement a Web Application Firewall (WAF) rule to block direct access to password-protected posts:

   location ~* /password-protected-post/ {
       return 403;
   }
   

3. Monitor logs for unauthorized access attempts.

Long-term Fix:

• Apply the official patch when released (check WordPress plugin repository).
• Replace the plugin with an alternative that properly handles authentication before content delivery.

Workaround:

• Use WordPress's built-in password protection with a custom page template that checks authentication before loading content.

Valters IT
DevSecOps & Cyber Threat Intelligence