CVE-2025-39348: Grand Restaurant Object Injection Flaw

CVE-2025-39348 Overview

CVE-2025-39348 is a critical Deserialization of Untrusted Data vulnerability affecting the ThemeGoods Grand Restaurant WordPress theme. This vulnerability allows attackers to perform PHP Object Injection attacks against vulnerable WordPress installations running affected versions of the theme. The flaw exists due to improper handling of serialized data, enabling unauthenticated remote attackers to inject malicious objects that can lead to complete site compromise.

Critical Impact

This vulnerability enables unauthenticated attackers to inject arbitrary PHP objects, potentially leading to remote code execution, data theft, or complete WordPress site takeover.

Affected Products

• ThemeGoods Grand Restaurant WordPress Theme versions through 7.0
• WordPress installations utilizing the Grand Restaurant theme
• Websites with Grand Restaurant theme installed regardless of activation status

Discovery Timeline

• 2025-05-19 - CVE CVE-2025-39348 published to NVD
• 2025-05-29 - Last updated in NVD database

Technical Details for CVE-2025-39348

Vulnerability Analysis

This vulnerability stems from insecure deserialization practices within the Grand Restaurant WordPress theme. When user-controlled input is passed to PHP's unserialize() function without proper validation, attackers can craft malicious serialized payloads that instantiate arbitrary PHP objects. Upon deserialization, these objects can trigger dangerous magic methods such as __wakeup(), __destruct(), or __toString(), leading to a variety of security impacts.

The attack requires no authentication and can be executed remotely over the network. Once exploited, an attacker may achieve arbitrary file operations, database manipulation, or full remote code execution depending on the available gadget chains within the WordPress installation and its plugins.

Root Cause

The root cause is classified under CWE-502 (Deserialization of Untrusted Data). The Grand Restaurant theme processes serialized data from untrusted sources without implementing adequate security controls. This allows attackers to control the class types and property values of deserialized objects, which can be weaponized through PHP Object Injection (POI) techniques.

WordPress themes and plugins often include classes with magic methods that can be abused as "gadget chains" to achieve code execution or other malicious outcomes when combined with an object injection vulnerability.

Attack Vector

The attack vector is network-based and requires no prior authentication or user interaction. An attacker can exploit this vulnerability by sending specially crafted HTTP requests containing malicious serialized PHP objects to the vulnerable WordPress site. The exploitation flow typically involves:

1. Identifying endpoints where the theme processes serialized data
2. Crafting a serialized payload with malicious object properties
3. Leveraging existing PHP classes (gadgets) in the WordPress ecosystem
4. Triggering dangerous operations through magic method execution

For detailed technical information about the vulnerability mechanism and exploitation, refer to the Patchstack WordPress Vulnerability Report.

Detection Methods for CVE-2025-39348

Indicators of Compromise

• Unusual HTTP requests containing base64-encoded or URL-encoded serialized PHP data patterns (e.g., O:, a:, s: prefixes)
• Unexpected file creation or modification in WordPress directories
• Suspicious database queries or new administrator accounts
• Web server logs showing POST requests with abnormally large or encoded payloads targeting theme endpoints

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block serialized PHP object patterns in request parameters
• Deploy WordPress security plugins that monitor for object injection attempts
• Enable verbose logging on the web server to capture suspicious request patterns
• Utilize SentinelOne Singularity platform for endpoint detection of post-exploitation activities

Monitoring Recommendations

• Monitor WordPress error logs for PHP unserialization warnings or fatal errors
• Set up alerts for unexpected file system changes in the wp-content/themes/grandrestaurant/ directory
• Track user account creation and privilege changes in WordPress
• Implement real-time monitoring for outbound connections from the web server that may indicate successful exploitation

How to Mitigate CVE-2025-39348

Immediate Actions Required

• Update the Grand Restaurant WordPress theme to a patched version if available from ThemeGoods
• Temporarily disable or remove the Grand Restaurant theme if no patch is available
• Implement WAF rules to block serialized PHP object patterns in HTTP requests
• Conduct a security audit of the WordPress installation to identify signs of compromise

Patch Information

Site administrators should check with ThemeGoods for an updated version of the Grand Restaurant theme that addresses this vulnerability. The vulnerability affects all versions through 7.0. Contact the vendor directly or check the theme marketplace where the theme was purchased for update availability. Additional details can be found in the Patchstack WordPress Vulnerability Report.

Workarounds

• Deploy a Web Application Firewall (WAF) with rules to filter serialized PHP object patterns in request data
• Implement input validation at the server level to reject requests containing suspicious serialization patterns
• Consider switching to an alternative WordPress theme until a security patch is released
• Restrict access to WordPress admin areas and theme functionality through IP whitelisting where possible

# Example .htaccess rule to block common serialized object patterns
# Add to WordPress root .htaccess file
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{QUERY_STRING} (O:|a:|s:)[0-9]+: [NC,OR]
RewriteCond %{REQUEST_BODY} (O:|a:|s:)[0-9]+: [NC]
RewriteRule .* - [F,L]
</IfModule>