CVE-2025-47581: WordPress Events Calendar Object Injection

CVE-2025-47581 Overview

CVE-2025-47581 is a critical deserialization of untrusted data vulnerability affecting the WordPress Events Calendar Registration & Tickets plugin by Elbisnero. This PHP Object Injection flaw allows unauthenticated attackers to inject arbitrary PHP objects through user-controlled input, potentially leading to remote code execution, unauthorized data access, or complete site compromise.

Critical Impact

Unauthenticated attackers can exploit this vulnerability remotely to inject malicious PHP objects, potentially achieving remote code execution on vulnerable WordPress installations without requiring user interaction.

Affected Products

• WordPress Events Calendar Registration & Tickets plugin versions up to and including 2.6.0
• WordPress installations running the vulnerable wpeventplus plugin
• Sites using the affected plugin without security hardening

Discovery Timeline

• 2025-05-19 - CVE-2025-47581 published to NVD
• 2025-05-21 - Last updated in NVD database

Technical Details for CVE-2025-47581

Vulnerability Analysis

This vulnerability falls under CWE-502 (Deserialization of Untrusted Data), a well-documented weakness where applications deserialize data from untrusted sources without proper validation. In the context of WordPress plugins, PHP object injection vulnerabilities arise when user-supplied serialized data is passed directly to unserialize() or similar functions.

When exploited, an attacker can craft malicious serialized PHP objects that, upon deserialization, trigger "magic methods" such as __wakeup(), __destruct(), or __toString(). If the WordPress installation contains classes with dangerous implementations of these magic methods (often called "POP gadgets"), the attacker can chain them together to achieve arbitrary code execution, file operations, or database manipulation.

The vulnerability requires no authentication or user interaction, making it particularly dangerous for internet-facing WordPress sites. The attack can be executed entirely over the network, and successful exploitation could lead to complete compromise of the affected WordPress installation including data theft, website defacement, or use of the server for further attacks.

Root Cause

The root cause of this vulnerability is the improper handling of serialized PHP data within the WordPress Events Calendar Registration & Tickets plugin. The plugin fails to validate or sanitize user-controlled input before passing it to PHP's deserialization functions, allowing attackers to inject arbitrary object structures.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can craft a malicious HTTP request containing specially serialized PHP objects targeting vulnerable endpoints in the plugin. The plugin processes this malicious input without proper validation, triggering the deserialization of attacker-controlled objects.

The vulnerability mechanism involves crafting serialized PHP payloads that exploit available POP (Property Oriented Programming) gadget chains within WordPress core or installed plugins. When the malicious serialized data is processed by the vulnerable plugin, the injected objects execute their magic methods, potentially leading to arbitrary code execution or other malicious outcomes.

For detailed technical analysis of this vulnerability, refer to the Patchstack WordPress Vulnerability Analysis.

Detection Methods for CVE-2025-47581

Indicators of Compromise

• Unexpected PHP serialized data patterns in web server access logs containing O: or a: prefixes
• Suspicious HTTP POST requests to plugin-specific endpoints with serialized payloads
• Anomalous file system changes or new PHP files appearing in the WordPress installation
• Unexpected outbound network connections from the web server
• Modified WordPress core files or plugin files with unauthorized changes

Detection Strategies

• Deploy Web Application Firewalls (WAF) with rules to detect and block serialized PHP object patterns in request parameters
• Monitor web server logs for requests containing serialized data signatures targeting the wpeventplus plugin endpoints
• Implement file integrity monitoring on WordPress installations to detect unauthorized modifications
• Use WordPress security plugins capable of detecting object injection attempts

Monitoring Recommendations

• Enable verbose logging on web servers to capture full request bodies for forensic analysis
• Configure real-time alerting for requests matching PHP serialization patterns
• Monitor server resource utilization for anomalies that may indicate active exploitation
• Review authentication logs for unauthorized administrative access following potential exploitation

How to Mitigate CVE-2025-47581

Immediate Actions Required

• Update WordPress Events Calendar Registration & Tickets plugin to a patched version if available
• If no patch is available, consider temporarily deactivating the plugin until a fix is released
• Implement WAF rules to block requests containing PHP serialized object patterns
• Review WordPress installation for signs of compromise if the vulnerable plugin was active
• Audit installed plugins and themes for additional POP gadget chains that could be exploited

Patch Information

Organizations should monitor the official plugin repository and the Patchstack security advisory for patch availability. Version 2.6.0 and all prior versions are confirmed vulnerable.

Workarounds

• Temporarily disable the WordPress Events Calendar Registration & Tickets plugin until a patch is available
• Implement server-level input filtering to block serialized PHP data in request parameters
• Use a Web Application Firewall with specific rules to detect and block object injection attempts
• Restrict access to WordPress admin and plugin endpoints using IP allowlisting where feasible
• Consider switching to an alternative events calendar plugin with a better security track record

# Example WAF rule for ModSecurity to block PHP serialized objects
SecRule ARGS "@rx [oOcC]:\d+:\"" "id:1001,phase:2,deny,status:403,msg:'PHP Object Injection Attempt Blocked'"