CVE-2025-31398: PIMP WordPress Object Injection Vulnerability

CVE-2025-31398 Overview

CVE-2025-31398 is a critical Insecure Deserialization vulnerability affecting the PIMP - Creative MultiPurpose WordPress theme by themeton. The vulnerability allows Object Injection through deserialization of untrusted data, enabling attackers to inject arbitrary PHP objects into the application. This issue affects all versions of the PIMP - Creative MultiPurpose theme from unknown versions through 1.7.

Critical Impact

Unauthenticated attackers can exploit this Object Injection vulnerability to achieve Remote Code Execution, data manipulation, or complete site takeover on WordPress installations running the vulnerable theme.

Affected Products

• PIMP - Creative MultiPurpose WordPress Theme versions through 1.7
• WordPress installations using the vulnerable theme
• Sites with PHP Magic Methods that can be chained for exploitation

Discovery Timeline

• 2025-06-09 - CVE-2025-31398 published to NVD
• 2025-06-12 - Last updated in NVD database

Technical Details for CVE-2025-31398

Vulnerability Analysis

This vulnerability falls under CWE-502 (Deserialization of Untrusted Data), which occurs when an application deserializes data from untrusted sources without proper validation. In the context of this WordPress theme, the application processes serialized PHP objects without verifying their integrity or origin.

The vulnerability is network-accessible and requires no authentication or user interaction to exploit. When an attacker submits a maliciously crafted serialized object, the PHP unserialize() function processes it, instantiating the attacker-controlled object. If the theme or any loaded plugins contain classes with exploitable magic methods (such as __destruct(), __wakeup(), or __toString()), an attacker can chain these methods to achieve arbitrary code execution, file operations, or database manipulation.

The impact encompasses full confidentiality, integrity, and availability compromise of the affected WordPress installation.

Root Cause

The root cause stems from the theme's use of PHP's unserialize() function on user-controllable input without implementing proper input validation or using secure alternatives. The application trusts incoming serialized data and processes it directly, allowing attackers to inject arbitrary PHP objects that execute malicious code upon deserialization.

Attack Vector

The attack is conducted over the network without requiring authentication. An attacker crafts a malicious serialized PHP object containing a Property-Oriented Programming (POP) chain. This chain exploits existing classes within the WordPress ecosystem that have dangerous magic methods.

When the malicious payload is submitted to a vulnerable endpoint, the theme's deserialization logic processes it, triggering the POP chain. Depending on the available gadget classes, this can result in arbitrary file writes, remote code execution, privilege escalation, or complete WordPress site takeover.

The exploitation process involves identifying a deserialization sink in the theme, discovering usable gadget classes in WordPress core, plugins, or the theme itself, constructing a POP chain, and delivering the payload through the vulnerable input vector.

Detection Methods for CVE-2025-31398

Indicators of Compromise

• Unusual serialized data patterns in web server access logs containing O: prefixes characteristic of PHP object serialization
• Unexpected PHP object instantiation errors in WordPress error logs
• New unknown files appearing in WordPress directories, particularly in writable locations like wp-content/uploads
• Modified WordPress core files or theme files with unexpected changes

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block serialized PHP object patterns in HTTP requests
• Monitor PHP error logs for deserialization-related warnings and fatal errors
• Deploy file integrity monitoring to detect unauthorized changes to WordPress files
• Analyze incoming HTTP request bodies for serialized object signatures (a:, O:, s: patterns)

Monitoring Recommendations

• Enable comprehensive logging on web servers to capture full request bodies for forensic analysis
• Configure alerting for suspicious patterns indicative of serialization attacks
• Implement real-time monitoring of WordPress file system changes
• Review authentication and session logs for signs of unauthorized access following exploitation

How to Mitigate CVE-2025-31398

Immediate Actions Required

• Disable or remove the PIMP - Creative MultiPurpose theme immediately if no patch is available
• Switch to a secure, well-maintained alternative WordPress theme
• Implement WAF rules to block requests containing serialized PHP objects targeting the vulnerable theme
• Conduct a security audit of the WordPress installation to identify any signs of prior compromise

Patch Information

Users should consult the Patchstack WordPress Vulnerability Report for the latest patch status and vendor remediation guidance. Monitor the theme developer's official channels for security updates addressing this vulnerability.

Workarounds

• Remove or deactivate the vulnerable theme and replace it with a secure alternative
• Implement input validation at the web server level using ModSecurity or similar WAF to block serialized object payloads
• Restrict access to the WordPress admin area using IP-based allowlisting
• Consider implementing PHP's allowed_classes parameter if custom code paths require deserialization functionality

# ModSecurity rule to block PHP serialized object patterns
SecRule REQUEST_BODY "@rx O:\d+:\"" "id:100001,phase:2,deny,status:403,msg:'Potential PHP Object Injection Attack'"

# Verify theme is disabled in WordPress
wp theme list --status=inactive --allow-root | grep pimp