CVE-2025-52827: Nuss Plugin Deserialization Vulnerability

CVE-2025-52827 Overview

CVE-2025-52827 is a PHP Object Injection vulnerability affecting the uxper Nuss WordPress theme. The flaw stems from deserialization of untrusted data [CWE-502] in versions up to and including 1.3.3. Authenticated attackers with low privileges can submit crafted serialized payloads that the theme passes to PHP's unserialize() function. Successful exploitation enables instantiation of arbitrary PHP objects, which can chain into remote code execution, file manipulation, or data exfiltration depending on available gadgets within the WordPress installation.

Critical Impact
Authenticated attackers can trigger PHP Object Injection to compromise confidentiality, integrity, and availability of WordPress sites running the Nuss theme through version 1.3.3.

Affected Products

uxper Nuss WordPress theme versions through 1.3.3
WordPress installations using the vulnerable Nuss theme
Any site with the affected theme active and accessible to authenticated users

Discovery Timeline

2025-06-27 - CVE-2025-52827 published to NVD
2026-04-23 - Last updated in NVD database

Technical Details for CVE-2025-52827

Vulnerability Analysis

The vulnerability resides in code paths within the Nuss theme that pass attacker-controlled input to PHP's unserialize() function. When PHP deserializes untrusted data, it reconstructs objects of arbitrary classes available in the application scope. This behavior allows attackers to trigger magic methods such as __wakeup(), __destruct(), and __toString() on chosen classes.

WordPress environments typically load many plugins and themes that define classes with side effects in their magic methods. Attackers chain these classes into POP (Property-Oriented Programming) gadgets to achieve arbitrary file operations, SQL execution, or command execution. The attack requires only low-privileged authentication, which lowers the barrier for exploitation across multi-author WordPress sites.

Root Cause

The root cause is improper handling of serialized data within the Nuss theme codebase. The theme deserializes input from request parameters, cookies, or stored options without validation or use of safe alternatives such as json_decode(). This violates secure deserialization practices defined in [CWE-502].

Attack Vector

The attack vector is network-based and requires low-privilege authentication. An attacker submits a crafted serialized PHP payload to a vulnerable endpoint exposed by the Nuss theme. The payload constructs a chain of objects whose destructor or wakeup logic invokes sensitive operations within other loaded WordPress components. The resulting impact depends on the gadget chains present, but commonly leads to remote code execution on the underlying web server.

For technical details on the disclosed vulnerability pattern, see the Patchstack WordPress Vulnerability Advisory.

Detection Methods for CVE-2025-52827

Indicators of Compromise

Unexpected PHP serialized strings beginning with O:, a:, or s: in HTTP request bodies, query strings, or cookies targeting Nuss theme endpoints
New or modified PHP files in wp-content/uploads/ or theme directories created shortly after suspicious authenticated requests
Unexpected WordPress administrator accounts or modifications to the wp_options table
Outbound connections from the web server to unknown hosts following exploitation attempts

Detection Strategies

Inspect web server and WordPress access logs for POST requests containing serialized object markers directed at theme-handled URLs
Deploy a Web Application Firewall (WAF) ruleset that detects PHP serialized payloads in request parameters
Monitor PHP error logs for __wakeup, __destruct, or class instantiation warnings originating from unexpected request contexts
Compare installed theme files against known-good hashes to detect tampering

Monitoring Recommendations

Enable file integrity monitoring on the wp-content/themes/nuss/ directory and core WordPress files
Forward WordPress, PHP-FPM, and web server logs to a centralized analytics platform for correlation
Alert on creation of new PHP files within upload directories and on changes to privileged user roles
Track authentication events for low-privilege accounts that subsequently issue requests to theme endpoints

How to Mitigate CVE-2025-52827

Immediate Actions Required

Identify all WordPress instances running the uxper Nuss theme at version 1.3.3 or earlier
Disable or remove the Nuss theme until a fixed version is installed if business operations permit
Audit user accounts and remove unused low-privilege accounts that could be leveraged for exploitation
Review recent file changes, scheduled tasks (wp_cron), and database entries for signs of compromise

Patch Information

At the time of publication, the advisory lists affected versions through 1.3.3 with no confirmed fixed release referenced in the NVD entry. Monitor the vendor and the Patchstack WordPress Vulnerability Advisory for an updated theme version, and apply it across all affected sites once released.

Workarounds

Restrict access to vulnerable theme endpoints using WAF rules that block serialized PHP payloads in request parameters
Apply principle of least privilege to WordPress accounts and disable self-registration where not required
Enforce strong authentication including multi-factor authentication for all WordPress users
Place the WordPress site behind an authenticated reverse proxy or IP allowlist for administrative paths until a patch is available

bash

# Example ModSecurity rule to detect PHP serialized object payloads in request bodies
SecRule REQUEST_BODY "@rx (?:^|[&=])(?:O|a|s):[0-9]+:\"" \
  "id:1005282,phase:2,deny,status:403,log,\
  msg:'Possible PHP Object Injection payload (CVE-2025-52827)'"