CVE-2026-23542: Grand Restaurant Object Injection Flaw

CVE-2026-23542 Overview

CVE-2026-23542 is an Insecure Deserialization vulnerability affecting the ThemeGoods Grand Restaurant WordPress theme. The vulnerability allows attackers to inject arbitrary PHP objects through untrusted data deserialization, potentially leading to remote code execution, data manipulation, or complete site compromise.

Critical Impact
Unauthenticated attackers can exploit this PHP Object Injection vulnerability to execute arbitrary code, modify database contents, or take complete control of affected WordPress installations running the Grand Restaurant theme.

Affected Products

ThemeGoods Grand Restaurant WordPress Theme versions through 7.0.10
WordPress installations using vulnerable Grand Restaurant theme versions

Discovery Timeline

2026-02-19 - CVE CVE-2026-23542 published to NVD
2026-02-19 - Last updated in NVD database

Technical Details for CVE-2026-23542

Vulnerability Analysis

This vulnerability stems from improper handling of serialized data within the Grand Restaurant WordPress theme. When the application deserializes user-controlled input without adequate validation, attackers can craft malicious serialized objects that, upon deserialization, trigger unintended code execution paths within the application.

PHP Object Injection vulnerabilities are particularly dangerous in WordPress environments due to the presence of numerous "magic methods" (__wakeup, __destruct, __toString) across the WordPress core, plugins, and themes. These methods execute automatically during object lifecycle events, creating potential "POP chains" (Property Oriented Programming chains) that attackers can leverage for remote code execution.

The attack requires no authentication, allowing any remote attacker to target vulnerable installations over the network. Successful exploitation can result in complete compromise of confidentiality, integrity, and availability of the affected WordPress site.

Root Cause

The root cause is classified as CWE-502: Deserialization of Untrusted Data. The Grand Restaurant theme fails to properly sanitize or validate serialized data before passing it to PHP's unserialize() function. This allows attackers to inject crafted serialized payloads containing malicious object properties that trigger dangerous operations when the objects are instantiated.

Attack Vector

The attack is network-based and requires no user interaction or prior authentication. An attacker can submit a crafted HTTP request containing a malicious serialized PHP object to a vulnerable endpoint within the Grand Restaurant theme. When the server deserializes this payload, the injected object's properties and magic methods execute in the context of the web server, potentially allowing arbitrary code execution.

The exploitation typically involves identifying gadget classes within the WordPress installation that contain exploitable magic methods, then constructing a serialized payload that chains these methods together to achieve code execution.

Detection Methods for CVE-2026-23542

Indicators of Compromise

Unusual serialized data patterns in HTTP request parameters, particularly containing PHP object notation (O: prefix)
Web server logs showing requests with base64-encoded or URL-encoded serialized payloads
Unexpected PHP files created in theme directories or uploads folder
Modified theme files or WordPress core files
Unauthorized administrator accounts or privilege changes

Detection Strategies

Monitor HTTP request bodies and parameters for serialized PHP object patterns (strings beginning with O:, a:, or s: followed by numeric values)
Deploy Web Application Firewall (WAF) rules to detect and block deserialization attack patterns
Implement file integrity monitoring on WordPress core, theme, and plugin directories
Review web server access logs for suspicious POST requests to theme-related endpoints
Enable WordPress debug logging to capture deserialization warnings

Monitoring Recommendations

Configure SIEM alerts for patterns indicative of PHP object injection attempts
Monitor for new file creation within the wp-content/themes/grandrestaurant/ directory structure
Track WordPress user creation and privilege escalation events
Implement real-time log analysis for web server access and error logs
Deploy endpoint detection solutions to monitor web server process behavior

How to Mitigate CVE-2026-23542

Immediate Actions Required

Update the Grand Restaurant theme to a patched version if available from ThemeGoods
If no patch is available, consider temporarily deactivating the theme and switching to a secure alternative
Implement WAF rules to block serialized PHP object payloads at the network perimeter
Review WordPress user accounts for unauthorized access or privilege changes
Perform a security audit of the WordPress installation for signs of compromise

Patch Information

Check the Patchstack Vulnerability Report for the latest patch status and remediation guidance from ThemeGoods. Contact the theme vendor directly for information about security updates addressing versions through 7.0.10.

Workarounds

Deploy a Web Application Firewall with rules specifically designed to detect and block PHP serialization attack patterns
Implement input validation at the server level to reject requests containing serialized object notation
Consider using WordPress security plugins that provide virtual patching capabilities for known vulnerabilities
Restrict access to WordPress admin and theme-related endpoints using IP allowlisting where feasible
Enable WordPress automatic updates to receive security patches promptly when released

bash

# Example WAF rule pattern for ModSecurity to detect PHP object injection
SecRule REQUEST_BODY "@rx [oOcC]:\d+:\"[a-zA-Z0-9_]+\":\d+:" \
    "id:100001,\
    phase:2,\
    deny,\
    status:403,\
    log,\
    msg:'PHP Object Injection Attempt Detected',\
    tag:'application-multi',\
    tag:'language-php',\
    tag:'platform-multi',\
    tag:'attack-injection-php'"