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

# 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'"