CVE-2025-47635

Executive Summary

CVE-2025-47635 is a Server-Side Request Forgery (SSRF) vulnerability in the WordPress plugin WebinarPress (slug: wp-webinarsystem), affecting versions up to and including 1.33.28. The flaw allows an unauthenticated attacker to make the server send crafted HTTP requests to internal or external resources, potentially leading to information disclosure, internal network scanning, or further exploitation. The CVSS score is 5.5 (Medium), and no official patch has been released by the vendor. The EPSS score is 0.0%, indicating low exploitation activity in the wild, but the risk remains significant for exposed WordPress installations.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin distributed via the official WordPress plugin repository. Users who installed the plugin via the WordPress dashboard or automated deployment tools are affected. No known malicious packages have been identified, but the lack of a patch increases supply chain risk for organizations relying on this plugin.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – The vulnerable component and the affected resource are the same.
• Confidentiality (C): Low (L) – Limited information disclosure possible.
• Integrity (I): None (N) – No data modification.
• Availability (A): None (N) – No denial of service.

Threat Level: Medium. While the CVSS score is moderate, SSRF can be chained with other vulnerabilities (e.g., internal service exploitation) to escalate impact.

Deep Dive & Mechanics

The vulnerability exists in the wp-webinarsystem plugin’s AJAX handler for webinar registration. The plugin fails to validate or sanitize user-supplied URLs passed to a server-side HTTP request function. An attacker can craft a request to the vulnerable endpoint, specifying an arbitrary URL (e.g., http://169.254.169.254/latest/meta-data/ for cloud metadata) that the server will fetch and return the response.

Root Cause: The plugin uses wp_remote_get() or similar functions with user-controlled input without proper URL validation or allowlisting.

Attack Flow:

1. Attacker identifies a WordPress site with WebinarPress installed.
2. Attacker sends a POST request to /wp-admin/admin-ajax.php with action parameter wpws_register and a crafted webinar_url parameter pointing to an internal resource.
3. The server executes the request and returns the response to the attacker.

Vulnerable vs. Patched Code

Vulnerable Code (simplified):

add_action('wp_ajax_nopriv_wpws_register', 'wpws_register_callback');
function wpws_register_callback() {
    $url = $_POST['webinar_url'];
    $response = wp_remote_get($url);
    echo wp_remote_retrieve_body($response);
    wp_die();
}

Patched Code (hypothetical):

add_action('wp_ajax_nopriv_wpws_register', 'wpws_register_callback');
function wpws_register_callback() {
    $url = esc_url_raw($_POST['webinar_url']);
    if (wp_http_validate_url($url) && !wp_http_is_internal_url($url)) {
        $response = wp_remote_get($url);
        echo wp_remote_retrieve_body($response);
    } else {
        echo 'Invalid URL';
    }
    wp_die();
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress instance with WebinarPress <= 1.33.28.
• Network access to the target.

Exploitation Steps:

1. Identify the vulnerable endpoint:

   curl -s "http://target/wp-admin/admin-ajax.php" -d "action=wpws_register&webinar_url=http://169.254.169.254/latest/meta-data/"
   

2. If successful, the response will contain cloud metadata (e.g., AWS IAM credentials).
3. For internal network scanning, use:

   curl -s "http://target/wp-admin/admin-ajax.php" -d "action=wpws_register&webinar_url=http://192.168.1.1:80/"
   

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

Blue Team

Detection & Response:

• Monitor for unusual admin-ajax.php requests with action=wpws_register and suspicious webinar_url parameters.
• Block outbound requests to internal IP ranges (RFC 1918) from the web server.
• Implement Web Application Firewall (WAF) rules to filter SSRF patterns.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Outbound HTTP requests from the web server to internal IPs (e.g., 10.x.x.x, 172.16.x.x, 192.168.x.x).
  • Requests to cloud metadata endpoints (e.g., 169.254.169.254).
• File IOCs:
  • Modified wp-content/plugins/wp-webinarsystem/ files (if attacker uploads webshell).
• Log IOCs:
  • Repeated admin-ajax.php requests with action=wpws_register and non-standard webinar_url values.

Detection Engineering

YARA Rule

rule CVE_2025_47635_WebinarPress_SSRF {
    meta:
        description = "Detects SSRF exploitation attempts against WebinarPress plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-47635"
    strings:
        $ajax_action = "action=wpws_register"
        $url_param = "webinar_url="
        $internal_ip = /(10\.\d{1,3}\.\d{1,3}\.\d{1,3}|172\.(1[6-9]|2[0-9]|3[01])\.\d{1,3}\.\d{1,3}|192\.168\.\d{1,3}\.\d{1,3}|169\.254\.\d{1,3}\.\d{1,3})/
    condition:
        $ajax_action and $url_param and $internal_ip
}

Sigma Rule

title: WebinarPress SSRF Exploitation Attempt
id: 8a9b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects SSRF attempts against WebinarPress plugin via admin-ajax.php
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query: 'admin-ajax.php'
        cs-uri-query|contains: 'action=wpws_register'
        cs-uri-query|contains: 'webinar_url='
        cs-uri-query|re: '(10\.\d{1,3}\.\d{1,3}\.\d{1,3}|172\.(1[6-9]|2[0-9]|3[01])\.\d{1,3}\.\d{1,3}|192\.168\.\d{1,3}\.\d{1,3}|169\.254\.\d{1,3}\.\d{1,3})'
    condition: selection
falsepositives:
    - Legitimate use of external webinar URLs (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-47635 WebinarPress SSRF Attempt"; flow:to_server,established; content:"POST"; http_method; content:"admin-ajax.php"; http_uri; content:"action=wpws_register"; http_client_body; content:"webinar_url="; http_client_body; pcre:"/(10\.\d{1,3}\.\d{1,3}\.\d{1,3}|172\.(1[6-9]|2[0-9]|3[01])\.\d{1,3}\.\d{1,3}|192\.168\.\d{1,3}\.\d{1,3}|169\.254\.\d{1,3}\.\d{1,3})/Ri"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the WebinarPress plugin if not critical to operations.
2. Implement a Web Application Firewall (WAF) rule to block requests containing webinar_url= with internal IP patterns.
3. Restrict outbound HTTP traffic from the web server using firewall rules (e.g., allow only necessary external domains).

Long-term Fix:

• Since no patch is available, consider migrating to an alternative webinar plugin.
• Monitor the vendor’s repository for updates and apply immediately when released.

Valters IT Signature This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.