CVE-2026-25400: Apicona Object Injection Vulnerability

CVE-2026-25400 Overview

CVE-2026-25400 is a Deserialization of Untrusted Data vulnerability affecting the thememount Apicona WordPress theme. This security flaw allows attackers to perform PHP Object Injection attacks, potentially leading to arbitrary code execution, data manipulation, or complete site compromise. The vulnerability exists in Apicona theme versions up to and including 24.1.0.

Critical Impact

Successful exploitation of this PHP Object Injection vulnerability could allow authenticated attackers with low privileges to execute arbitrary code, access sensitive data, or gain complete control over affected WordPress installations.

Affected Products

• Apicona WordPress Theme versions through 24.1.0
• thememount Apicona theme installations on WordPress

Discovery Timeline

• 2026-03-25 - CVE-2026-25400 published to NVD
• 2026-03-26 - Last updated in NVD database

Technical Details for CVE-2026-25400

Vulnerability Analysis

This vulnerability stems from improper handling of serialized data within the Apicona WordPress theme. When user-controlled input is passed to PHP's unserialize() function without proper validation, attackers can inject malicious serialized objects that execute arbitrary operations when deserialized.

PHP Object Injection vulnerabilities are particularly dangerous in WordPress environments because the presence of various classes with "magic methods" (such as __wakeup(), __destruct(), or __toString()) can be chained together to form Property-Oriented Programming (POP) chains. These chains allow attackers to achieve Remote Code Execution, file manipulation, SQL injection, or other malicious outcomes depending on the classes available in the application context.

Root Cause

The root cause is classified under CWE-502 (Deserialization of Untrusted Data). The Apicona theme fails to properly validate or sanitize serialized data before processing it through PHP's deserialization functions. This allows attackers to craft malicious serialized payloads that, when processed by the application, instantiate arbitrary objects and trigger dangerous method calls.

Attack Vector

The attack is network-based and requires low-privilege authentication to exploit. An attacker with a valid WordPress account (such as a subscriber or contributor role) can submit specially crafted serialized PHP objects through vulnerable input points in the Apicona theme. When the theme deserializes this malicious input, the attacker's payload executes within the context of the WordPress application.

The exploitation process typically involves:

1. Identifying available PHP classes within the WordPress installation and theme
2. Constructing a POP chain using classes with exploitable magic methods
3. Serializing the malicious object chain
4. Submitting the payload through vulnerable theme functionality
5. The application deserializes the payload, triggering the attack chain

For detailed technical information about this vulnerability, refer to the Patchstack WordPress Vulnerability Report.

Detection Methods for CVE-2026-25400

Indicators of Compromise

• Unusual PHP serialized strings in HTTP request parameters, especially containing class names or nested objects
• Web server logs showing requests with base64-encoded or URL-encoded serialized PHP data
• Unexpected file creation or modification in WordPress directories
• New or modified user accounts with elevated privileges
• Suspicious outbound network connections from the web server

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block requests containing PHP serialized object patterns
• Monitor WordPress logs for authentication events from accounts performing unusual administrative actions
• Deploy file integrity monitoring on WordPress core files, theme files, and upload directories
• Review web server access logs for requests with unusually long parameters or suspicious encoded content

Monitoring Recommendations

• Enable comprehensive logging for WordPress authentication and plugin/theme activity
• Configure real-time alerting for changes to critical WordPress files and database tables
• Monitor for new PHP files being created in theme or upload directories
• Implement network traffic analysis to detect command-and-control communications

How to Mitigate CVE-2026-25400

Immediate Actions Required

• Update the Apicona theme to the latest patched version immediately
• Review WordPress user accounts for unauthorized accounts or privilege escalations
• Audit recent file changes on the WordPress installation for signs of compromise
• Temporarily disable the Apicona theme if an update is not available and switch to a default WordPress theme

Patch Information

Site administrators should check for updates from thememount for the Apicona WordPress theme. Consult the Patchstack WordPress Vulnerability Report for the latest remediation guidance and version information.

Workarounds

• Implement strict input validation at the application level to reject serialized PHP data from user input
• Deploy a Web Application Firewall configured to block requests containing PHP serialization patterns
• Restrict user registration and minimize the number of authenticated users on the WordPress site
• Consider using WordPress security plugins that provide object injection protection
• Harden file permissions to prevent unauthorized file writes even if exploitation occurs

# Example: Restrict WordPress file permissions
find /var/www/html/wordpress -type d -exec chmod 755 {} \;
find /var/www/html/wordpress -type f -exec chmod 644 {} \;
chown -R www-data:www-data /var/www/html/wordpress
chmod 400 /var/www/html/wordpress/wp-config.php