CVE-2025-58244

Executive Summary

CVE-2025-58244 is a Cross-Site Request Forgery (CSRF) vulnerability in the Anps Constructo WordPress theme, affecting versions up to and including 4.3.9. This flaw allows an unauthenticated attacker to trick a logged-in administrator into performing unintended actions, specifically enabling Object Injection. The attack vector relies on social engineering to make the admin click a crafted link or visit a malicious page while authenticated. Successful exploitation can lead to arbitrary object injection, potentially resulting in remote code execution or complete site compromise. The vulnerability is currently unpatched, and no public proof-of-concept (PoC) or exploit code is available. The EPSS score is 0.0%, indicating low exploitation likelihood in the wild, but the high CVSS score (8.8) demands immediate attention.

Supply Chain & Package Security

This vulnerability affects the WordPress ecosystem via the Anps Constructo theme. Since it is a commercial theme, users must rely on the vendor for patches. No open-source package (NPM, PyPI, Go, Ruby) is involved, but the theme may include bundled JavaScript libraries that could be leveraged in CSRF attacks. Administrators should audit all active plugins and themes for similar CSRF issues.

CVSS Breakdown & Threat Level

• CVSS Score: 8.8 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
• Attack Vector (AV): Network – exploitable remotely.
• Attack Complexity (AC): Low – no special conditions required.
• Privileges Required (PR): None – attacker does not need authentication.
• User Interaction (UI): Required – victim must click a link or visit a page.
• Scope (S): Unchanged – exploitation does not affect other components.
• Confidentiality (C): High – potential data exposure.
• Integrity (I): High – arbitrary object injection can modify site data.
• Availability (A): High – could lead to site defacement or denial of service.

Threat Level: High. Although no active exploitation is reported, the lack of a patch and the potential for object injection make this a critical risk for WordPress sites using the Constructo theme.

Deep Dive & Mechanics

The vulnerability resides in the Constructo theme's administrative interface, where state-changing operations (e.g., saving settings, importing/exporting data) lack proper CSRF tokens. An attacker can craft a malicious HTML page or email that, when visited by an authenticated admin, triggers a forged request to the WordPress admin area. This request can exploit PHP object injection via unserialize() calls in the theme's code, allowing the attacker to inject arbitrary PHP objects. If a suitable gadget chain exists (e.g., via WordPress core or other plugins), this can escalate to remote code execution.

Key Technical Details:

• CSRF Vector: The theme does not validate the _wpnonce or custom CSRF tokens for certain AJAX or form submissions.
• Object Injection: The injected data is passed to unserialize() or similar functions without sanitization, enabling arbitrary object instantiation.
• Prerequisite: The attacker must know the target admin's URL and have a way to deliver the CSRF payload (e.g., via a phishing email or malicious ad).

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to be in the theme's admin functions. A typical vulnerable pattern might look like:

Vulnerable Code (constructo/admin/options.php):

function constructo_save_settings() {
    // No CSRF check
    $data = $_POST['theme_options'];
    update_option('constructo_options', unserialize(base64_decode($data)));
}

Patched Code (hypothetical):

function constructo_save_settings() {
    if ( ! isset( $_POST['_wpnonce'] ) || ! wp_verify_nonce( $_POST['_wpnonce'], 'constructo_save_settings' ) ) {
        wp_die( 'CSRF validation failed.' );
    }
    $data = sanitize_text_field( $_POST['theme_options'] );
    update_option( 'constructo_options', $data );
}

The patch would add a nonce check and avoid using unserialize() on user input.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Install WordPress with the Constructo theme (version 4.3.9) on a local server (e.g., XAMPP or Docker).
2. Create an admin user and log in.
3. Prepare a malicious HTML page that triggers the CSRF.

Exploitation Steps:

1. Craft a CSRF payload that sends a POST request to the vulnerable endpoint (e.g., /wp-admin/admin-ajax.php?action=constructo_save).
2. Host the HTML page on an attacker-controlled server.
3. Send the link to the admin via email or social engineering.
4. When the admin clicks the link while logged in, the payload executes, injecting a malicious PHP object.

Example CSRF HTML Payload:

<html>
<body>
<form action="http://target-site.com/wp-admin/admin-ajax.php" method="POST">
    <input type="hidden" name="action" value="constructo_save" />
    <input type="hidden" name="theme_options" value="TzoxMDoiV3BfT2JqZWN0X0NvbGxlY3Rpb24iOjA6e30=" />
    <input type="submit" value="Click me" />
</form>
<script>document.forms[0].submit();</script>
</body>
</html>

Note: The base64-encoded value is a serialized PHP object. Replace with a real gadget chain for RCE.

Blue Team (Defensive)

Detection:

• Monitor for unusual POST requests to admin-ajax.php or theme-specific endpoints without a valid nonce.
• Look for base64-encoded strings in POST parameters that decode to serialized PHP objects.
• Use web application firewalls (WAF) to block requests with suspicious unserialize patterns.

Prevention:

• Implement CSRF tokens (nonces) for all admin actions.
• Avoid using unserialize() on user input; use JSON or sanitized data instead.
• Restrict admin access to trusted IPs and enforce strong authentication.

Indicators of Compromise (IOCs)

• Network IOCs:
  • POST requests to /wp-admin/admin-ajax.php with action=constructo_save or similar.
  • Base64-encoded strings in theme_options or similar parameters.
  • Referer headers from external domains (CSRF origin).
• File IOCs:
  • Unexpected PHP files in wp-content/uploads/ or wp-content/themes/constructo/.
  • Modified wp-config.php or .htaccess files.
• System IOCs:
  • New admin users created without authorization.
  • Unusual database entries in wp_options (e.g., constructo_options containing serialized objects).

Detection Engineering

YARA Rule

rule CVE_2025_58244_CSRF_Object_Injection {
    meta:
        description = "Detects CSRF-based object injection attempts targeting Constructo theme"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-58244"
    strings:
        $csrf_action = "constructo_save" nocase
        $serialized_pattern = /[a-zA-Z0-9+\/=]{20,}/  // base64-like
        $unserialize_call = "unserialize" nocase
    condition:
        $csrf_action and ($serialized_pattern or $unserialize_call)
}

Sigma Rule

title: CVE-2025-58244 CSRF Object Injection Attempt
id: 8a4b3c2d-1e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects HTTP POST requests targeting Constructo theme admin endpoints with potential serialized payloads
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'admin-ajax.php'
        cs-uri-query|contains: 'action=constructo_save'
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-58244 CSRF Object Injection Attempt"; flow:to_server,established; content:"POST"; http_method; content:"admin-ajax.php"; http_uri; content:"action=constructo_save"; http_client_body; pcre:"/[a-zA-Z0-9+\/=]{40,}/"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Constructo theme if possible and switch to a secure alternative.
2. Implement a Web Application Firewall (WAF) rule to block requests to admin-ajax.php without a valid nonce.
3. Restrict admin access to trusted IPs and enforce multi-factor authentication (MFA).

Long-Term Fix:

• Vendor Patch: Await an official patch from Anps. Contact the vendor for an ETA.
• Manual Patching: If you have access to the theme source code, add CSRF nonce checks to all admin-facing functions and replace unserialize() with safer alternatives like json_decode().
• Monitor: Continuously monitor logs for CSRF attempts and object injection patterns.

Workaround:

• Use a security plugin (e.g., Wordfence) to add CSRF protection to all admin actions.
• Disable the theme's AJAX functionality if not essential.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert