CVE-2026-42380: AI Lab PHP Object Injection Vulnerability

CVE-2026-42380 Overview

CVE-2026-42380 is an unauthenticated PHP Object Injection vulnerability affecting the AI Lab WordPress theme in versions prior to 5.4.2. The flaw stems from insecure deserialization of attacker-controlled input [CWE-502], allowing remote attackers to inject crafted PHP objects without authentication. When the application unserializes hostile data, existing PHP classes (gadgets) can be abused to trigger code execution, file operations, or other unintended behavior. The vulnerability is exposed over the network with low attack complexity and requires no user interaction.

Critical Impact
Unauthenticated remote attackers can deserialize malicious payloads against WordPress sites running the AI Lab theme, potentially leading to remote code execution and full site compromise.

Affected Products

AI Lab WordPress theme versions prior to 5.4.2
WordPress installations using the vulnerable AI Lab theme
Any site exposing endpoints that pass user input to PHP unserialize()

Discovery Timeline

2026-06-17 - CVE-2026-42380 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2026-42380

Vulnerability Analysis

The AI Lab theme processes serialized PHP data from untrusted sources without validation. PHP Object Injection occurs when user-supplied input is passed to unserialize(), allowing attackers to instantiate arbitrary classes that are loaded in the application context. If any reachable class implements magic methods such as __wakeup, __destruct, or __toString, attackers can chain these into a property-oriented programming (POP) gadget chain.

WordPress environments amplify this risk because core, plugins, and other themes load numerous classes into the same execution context. Attackers can reuse gadgets from any loaded component to escalate object injection into file writes, arbitrary SQL, or command execution. The vulnerability requires no authentication, which means external scanners and automated bots can target exposed WordPress sites at scale.

Root Cause

The root cause is improper handling of serialized data passed through theme functionality. The vulnerable code path invokes deserialization on input that originates from HTTP requests, cookies, or other client-controlled channels. Without an allow-list of expected types or signed payloads, PHP reconstructs attacker-chosen objects with attacker-defined properties.

Attack Vector

An unauthenticated remote attacker crafts a serialized PHP payload referencing a gadget chain present in WordPress core, the AI Lab theme, or other installed plugins. The attacker delivers this payload through a public request handled by the theme. On the server, PHP unserializes the payload and triggers the gadget chain during object lifecycle events, achieving the attacker's objective without credentials or user interaction. Refer to the Patchstack WordPress Vulnerability Advisory for vendor-specific details.

Detection Methods for CVE-2026-42380

Indicators of Compromise

HTTP request bodies, query strings, or cookies containing serialized PHP markers such as O: (object), a: (array), or s: (string) followed by class names.
Web server access logs showing repeated POST requests to AI Lab theme endpoints from a single source.
New or modified PHP files in the WordPress webroot, especially in wp-content/uploads/ or theme directories.
Unexpected outbound network connections initiated by the PHP-FPM or web server process.

Detection Strategies

Inspect web application firewall (WAF) and reverse proxy logs for serialized object patterns matching O:[0-9]+:"[A-Za-z_\\]+": in request parameters.
Hunt for PHP processes spawning shell utilities such as sh, bash, wget, or curl from the web server user context.
Monitor WordPress file integrity to detect unauthorized creation or modification of .php files under theme and upload directories.

Monitoring Recommendations

Enable verbose access logging on the web tier and forward logs to a SIEM for correlation against known PHP Object Injection signatures.
Alert on anomalous user-agent strings or burst traffic targeting WordPress theme endpoints.
Track outbound connections from PHP workers to non-corporate destinations, which often indicate post-exploitation callbacks.

How to Mitigate CVE-2026-42380

Immediate Actions Required

Upgrade the AI Lab WordPress theme to version 5.4.2 or later on all affected sites.
Audit WordPress installations for unauthorized administrative accounts, scheduled tasks, and modified theme or plugin files.
Rotate WordPress secrets in wp-config.php (AUTH_KEY, SECURE_AUTH_KEY, LOGGED_IN_KEY, NONCE_KEY) and reset administrator credentials if compromise is suspected.

Patch Information

The vendor has released AI Lab theme version 5.4.2, which addresses the unauthenticated PHP Object Injection issue. Administrators should apply the update through the WordPress theme management interface or by replacing theme files manually. Validate the patch by confirming the installed theme version after deployment. See the Patchstack WordPress Vulnerability Advisory for advisory details.

Workarounds

Place the WordPress site behind a WAF with rules that block serialized PHP payloads in untrusted request parameters.
Restrict access to AI Lab theme endpoints via IP allow-listing or authentication at the reverse proxy where feasible.
Disable the AI Lab theme and switch to an unaffected theme until patching is complete.

bash

# Configuration example: verify installed AI Lab theme version via WP-CLI
wp theme list --format=table | grep -i ailab
wp theme update ailab --version=5.4.2