CVE-2026-22501: Mounthood Object Injection Vulnerability

CVE-2026-22501 Overview

A Deserialization of Untrusted Data vulnerability has been identified in the axiomthemes Mounthood WordPress theme that allows Object Injection attacks. This vulnerability affects the Mounthood theme from all versions through 1.3.2. The flaw enables attackers to inject arbitrary PHP objects through unsanitized user input, potentially leading to severe security impacts including remote code execution, data manipulation, or complete site compromise.

Critical Impact

Attackers can exploit this PHP Object Injection vulnerability to execute arbitrary code, access sensitive data, or take complete control of affected WordPress installations running the vulnerable Mounthood theme.

Affected Products

• axiomthemes Mounthood WordPress Theme version 1.3.2 and earlier
• WordPress installations using the Mounthood theme
• All Mounthood theme versions from initial release through 1.3.2

Discovery Timeline

• 2026-03-05 - CVE-2026-22501 published to NVD
• 2026-03-05 - Last updated in NVD database

Technical Details for CVE-2026-22501

Vulnerability Analysis

This vulnerability is classified as CWE-502 (Deserialization of Untrusted Data), a particularly dangerous weakness in web applications. PHP Object Injection occurs when user-controllable data is passed to PHP's unserialize() function without proper validation or sanitization. When exploited, attackers can instantiate arbitrary PHP objects and potentially trigger dangerous "magic methods" such as __wakeup(), __destruct(), or __toString() that may be present in the application's codebase or its dependencies.

The Mounthood WordPress theme fails to properly validate serialized data before deserialization, creating an entry point for attackers to inject malicious object chains. Depending on the PHP classes available in the WordPress installation (including plugins and other themes), an attacker could leverage Property Oriented Programming (POP) chains to achieve various malicious outcomes.

Root Cause

The root cause of this vulnerability lies in the unsafe handling of serialized data within the Mounthood theme. The theme accepts serialized PHP data from user input and passes it directly to PHP's unserialize() function without implementing proper validation, whitelisting of allowed classes, or input sanitization. This architectural flaw allows attackers to craft malicious serialized objects that, when deserialized, can exploit existing class methods within the application context.

Attack Vector

The attack vector for this vulnerability involves an attacker crafting a malicious serialized PHP object payload and submitting it through an input mechanism processed by the vulnerable Mounthood theme. The exploitation process typically follows these steps:

1. The attacker identifies an input parameter that accepts serialized data in the Mounthood theme
2. A malicious serialized object is crafted, potentially chaining multiple class methods (POP chain)
3. The payload is submitted to the vulnerable endpoint
4. The Mounthood theme deserializes the untrusted data using unserialize()
5. PHP magic methods are triggered during object instantiation or destruction
6. Depending on available classes, the attacker achieves code execution, file manipulation, or data access

For detailed technical analysis and proof-of-concept information, see the Patchstack WordPress Vulnerability Database.

Detection Methods for CVE-2026-22501

Indicators of Compromise

• Unusual POST requests containing serialized PHP objects with unexpected class names
• Web server logs showing requests with base64-encoded or URL-encoded serialized data patterns (e.g., O:8:"ClassName":)
• Unexpected file creation or modification within WordPress directories
• Abnormal database queries or unauthorized administrative actions
• PHP error logs showing object instantiation errors for unexpected classes

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block serialized PHP object patterns in HTTP requests
• Monitor web server access logs for suspicious parameter values containing serialized data structures
• Deploy file integrity monitoring to detect unauthorized changes to theme files
• Review PHP error logs for deserialization-related warnings or class instantiation failures
• Utilize WordPress security plugins that scan for known vulnerability patterns

Monitoring Recommendations

• Enable comprehensive logging for all WordPress theme-related HTTP requests
• Set up alerts for requests containing PHP serialization patterns (O:[0-9]+: or a:[0-9]+:)
• Monitor for unusual outbound connections from the web server that may indicate successful exploitation
• Implement real-time file change monitoring for WordPress core, theme, and upload directories

How to Mitigate CVE-2026-22501

Immediate Actions Required

• Update the Mounthood theme to the latest patched version if available from axiomthemes
• If no patch is available, consider temporarily deactivating and removing the Mounthood theme
• Implement WAF rules to block requests containing serialized PHP objects
• Review server logs for potential exploitation attempts
• Conduct a security audit of the WordPress installation for signs of compromise

Patch Information

Administrators should check the Patchstack vulnerability database and the axiomthemes official website for patch availability. Until an official patch is released, implement the workarounds listed below to reduce exposure to this vulnerability.

Workarounds

• Temporarily replace the Mounthood theme with an alternative secure theme until a patch is available
• Implement server-level input filtering to block serialized PHP data in requests
• Deploy a Web Application Firewall with rules specifically targeting PHP object injection payloads
• Restrict access to the WordPress admin area and limit user registration if not required
• Consider implementing virtual patching through security plugins like Patchstack or Wordfence

To detect serialized PHP objects in web server requests, administrators can implement the following ModSecurity rule:

# ModSecurity rule to detect PHP serialized object patterns
SecRule REQUEST_BODY|ARGS "@rx O:\d+:\"[a-zA-Z_]" \
    "id:1001,\
    phase:2,\
    deny,\
    status:403,\
    msg:'Potential PHP Object Injection Attack Detected',\
    logdata:'Matched Data: %{MATCHED_VAR}',\
    severity:'CRITICAL'"