CVE-2022-4324 in Custom Field Template Plugin
Summary
by MITRE • 01/03/2023
The Custom Field Template WordPress plugin before 2.5.8 unserialises the content of an imported file, which could lead to PHP object injections issues when a high privilege user import (intentionally or not) a malicious Customizer Styling file and a suitable gadget chain is present on the blog.
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Analysis
by VulDB Data Team • 01/27/2023
The vulnerability identified as CVE-2022-4324 affects the Custom Field Template WordPress plugin version 2.5.7 and earlier, presenting a critical security risk through improper input validation and unsafe deserialization practices. This flaw enables attackers to execute arbitrary code on affected WordPress installations when a privileged user imports a malicious Customizer Styling file. The vulnerability stems from the plugin's failure to properly sanitize and validate the content of imported files before processing them through PHP's unserialization mechanism, creating a pathway for remote code execution.
The technical exploitation of this vulnerability relies on PHP object injection techniques where an attacker crafts a malicious file containing serialized PHP objects that, when imported, trigger unintended object instantiation. This process occurs during the import functionality of the Custom Field Template plugin, specifically when handling Customizer Styling files. The vulnerability is particularly dangerous because it requires only a high-privilege user to be tricked into importing the malicious file, which can be achieved through social engineering or by compromising an administrator account. The presence of suitable gadget chains within the WordPress installation or its dependencies amplifies the impact, allowing attackers to chain multiple vulnerabilities together for more sophisticated attacks.
From an operational perspective, this vulnerability creates a significant risk for WordPress site administrators who may unknowingly import malicious files through legitimate plugin functionality. The attack vector requires minimal user interaction beyond the standard import process, making it particularly dangerous in environments where administrators regularly import configuration files or themes. The impact extends beyond simple code execution to potentially allow full system compromise, data exfiltration, and persistent backdoor installation. This vulnerability directly aligns with CWE-502 which categorizes unsafe deserialization as a critical weakness, and it maps to ATT&CK technique T1546.004 for persistence mechanisms through web shell deployment.
Mitigation strategies for CVE-2022-4324 should prioritize immediate plugin updates to version 2.5.8 or later, which includes proper input validation and sanitization for imported files. Organizations should implement strict file validation policies that prevent import of untrusted files, particularly those with custom extensions or originating from unknown sources. Network segmentation and privileged account protection measures should be enforced to limit the potential impact of successful exploitation. Additionally, monitoring for unusual import activities and implementing automated security scanning tools can help detect and prevent malicious file imports. Regular security audits of WordPress plugins and themes should include verification of deserialization practices and input validation mechanisms to prevent similar vulnerabilities from emerging in other components of the web application stack.