CVE-2016-7169 in WordPress
Summary
by MITRE
Directory traversal vulnerability in the File_Upload_Upgrader class in wp-admin/includes/class-file-upload-upgrader.php in the upgrade package uploader in WordPress before 4.6.1 allows remote authenticated users to access arbitrary files via a crafted urlholder parameter.
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Analysis
by VulDB Data Team • 10/27/2022
The vulnerability CVE-2016-7169 represents a directory traversal flaw within WordPress's upgrade package uploader functionality, specifically affecting versions prior to 4.6.1. This issue resides in the File_Upload_Upgrader class located in wp-admin/includes/class-file-upload-upgrader.php, which handles file uploads during WordPress core upgrades. The vulnerability arises from insufficient input validation when processing the urlholder parameter, which is used to specify the location of upgrade packages. Attackers can exploit this weakness by crafting malicious urlholder values that contain directory traversal sequences such as ../ or ..\, allowing them to navigate outside the intended directory structure and access arbitrary files on the server. This vulnerability is particularly dangerous because it affects authenticated users who have the capability to upload files, meaning that any user with appropriate permissions can potentially exploit this flaw to gain unauthorized access to sensitive system files, configuration data, or other restricted resources. The flaw demonstrates a classic path traversal vulnerability that falls under CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. These attacks are categorized under the ATT&CK technique T1059.001 for command and scripting interpreter and T1083 for file and directory discovery, as they enable attackers to explore the filesystem and potentially extract sensitive information.
The operational impact of this vulnerability extends beyond simple file access, as it can lead to complete system compromise when combined with other attack vectors. An authenticated attacker with upload privileges could potentially access WordPress configuration files containing database credentials, plugin configurations, or other sensitive data that could be used for further exploitation. The vulnerability specifically affects the upgrade package functionality, which means it could be exploited during legitimate WordPress updates, providing an attacker with a plausible cover for malicious activity. Attackers might also be able to access PHP files that contain sensitive information, or potentially gain access to other system files that could reveal system architecture, user permissions, or other intelligence useful for deeper attacks. The attack surface is particularly concerning because WordPress installations often run with elevated privileges, and the ability to traverse directories could potentially allow access to system files or other applications running on the same server. This vulnerability directly impacts the principle of least privilege, as it allows authenticated users to bypass normal file access controls and access files they should not be permitted to read. The flaw also represents a failure in input sanitization and validation, which are fundamental security practices that should be implemented at multiple layers of application security.
Mitigation strategies for CVE-2016-7169 primarily focus on immediate patching and implementation of proper input validation. WordPress administrators should immediately upgrade to version 4.6.1 or later, which contains the necessary fixes to address the directory traversal vulnerability. Beyond patching, organizations should implement additional security controls such as input validation on all parameters that accept file paths or URLs, particularly those used in file handling operations. The implementation of proper path validation should include sanitizing input parameters, using allowlists of acceptable paths, and ensuring that all file operations occur within designated safe directories. Security measures should also include monitoring for unusual file access patterns, particularly around upgrade and upload functionality, and implementing proper access controls to limit which users can perform upgrade operations. Organizations should also consider implementing web application firewalls that can detect and block directory traversal attempts, as well as regular security audits of file handling code to identify similar vulnerabilities. The fix implemented in WordPress 4.6.1 likely includes proper validation of the urlholder parameter to prevent directory traversal sequences from being processed, ensuring that all file paths are properly validated against a whitelist of acceptable locations. Additionally, security best practices recommend implementing the principle of least privilege for file operations, ensuring that the application runs with minimal necessary permissions and that file access is restricted to only required directories. This vulnerability highlights the importance of proper security testing and code review processes, particularly for applications that handle file operations and user-provided input, as such flaws can have severe consequences for system security and data integrity.