CVE-2018-20147 in WordPress
Summary
by MITRE
In WordPress versions before 5.0.1, authors could modify metadata to bypass intended restrictions on deleting files.
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Analysis
by VulDB Data Team • 06/19/2023
This vulnerability exists within the WordPress content management system where unauthorized users with author privileges can manipulate metadata to circumvent file deletion restrictions that are typically enforced for lower-privilege accounts. The flaw specifically affects WordPress versions prior to 5.0.1 and represents a critical access control bypass issue that undermines the security model designed to protect file system operations. The vulnerability stems from insufficient validation of metadata fields during file deletion operations, allowing malicious actors to inject crafted metadata that modifies the system's permission checks. This weakness directly violates the principle of least privilege and creates an avenue for potential privilege escalation within the WordPress environment. The technical implementation of this flaw involves the manipulation of file metadata attributes that are used to determine whether a user has sufficient permissions to perform deletion operations, effectively allowing authors to bypass the normal administrative checks that should prevent them from removing files they do not own.
The operational impact of this vulnerability extends beyond simple unauthorized file deletion as it provides a foundation for more sophisticated attacks within the WordPress ecosystem. An attacker with author-level access could leverage this flaw to remove critical system files, modify core WordPress components, or delete content that would normally be protected from their access level. This vulnerability particularly affects multi-user WordPress installations where authors have limited privileges but should not be able to perform administrative operations. The flaw creates a persistent security risk that remains active until the WordPress installation is upgraded to version 5.0.1 or later, making it a significant concern for organizations maintaining older WordPress deployments. Security researchers have classified this vulnerability under CWE-284 which specifically addresses improper access control, and it aligns with ATT&CK technique T1078 which covers valid accounts and privilege escalation through unauthorized access to system resources.
Organizations should implement immediate mitigations including mandatory upgrades to WordPress 5.0.1 or later versions, which contain the necessary patches to address the metadata validation issues. System administrators should also review and audit user permissions to ensure that author accounts do not have unnecessary file system access capabilities. Additional protective measures include implementing web application firewalls that can detect and block suspicious metadata manipulation attempts, monitoring file deletion activities for unusual patterns, and maintaining regular backups to facilitate recovery from potential malicious file removals. The vulnerability highlights the importance of proper input validation and metadata handling in web applications, particularly in content management systems where user privileges must be strictly enforced. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and reduce the window of exposure for known vulnerabilities. This particular flaw demonstrates how seemingly minor permission validation issues can create significant security risks in complex web applications, emphasizing the need for comprehensive security testing and continuous vulnerability assessment procedures.