CVE-2015-9338 in wp-file-upload Plugin
Summary
by MITRE
The wp-file-upload plugin before 2.5.0 for WordPress has insufficient restrictions on upload of .php files.
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Analysis
by VulDB Data Team • 11/28/2023
The wp-file-upload plugin vulnerability represents a critical security flaw in WordPress plugin ecosystems that has persisted for years. This issue affects versions prior to 2.5.0 of the wp-file-upload plugin, which is widely used across WordPress installations for file management capabilities. The vulnerability stems from inadequate input validation and file type checking mechanisms within the plugin's upload functionality. Attackers can exploit this weakness to upload malicious php files that can execute arbitrary code on the target server, potentially leading to complete system compromise. The vulnerability is particularly dangerous because it directly targets the core file upload functionality that many WordPress sites rely upon for legitimate operations.
The technical implementation of this flaw demonstrates a classic insufficient validation issue that aligns with CWE-434, which describes the improper restriction of uploads of executable files. The plugin fails to properly validate file extensions, content types, or file signatures, allowing attackers to bypass security measures designed to prevent php file uploads. This weakness exists in the plugin's core file handling logic where it does not adequately verify that uploaded files conform to expected file types or contain malicious code. The vulnerability operates at the application layer and can be exploited through standard web application attack vectors, making it accessible to threat actors with minimal technical expertise. The flaw essentially creates a backdoor in the WordPress file management system that can be leveraged for various malicious activities including data exfiltration, system compromise, or deployment of additional malware.
The operational impact of this vulnerability extends beyond simple code execution, as it enables attackers to establish persistent access to compromised WordPress installations. Once an attacker successfully uploads a malicious php file, they can use it to create web shells, steal sensitive data, modify website content, or launch further attacks against internal networks. The vulnerability affects not only the immediate WordPress installation but also potentially the entire hosting environment if proper isolation measures are not in place. This type of vulnerability is particularly concerning in shared hosting environments where multiple websites share the same infrastructure, as a compromise of one site can potentially affect others. The attack surface is amplified by the widespread adoption of the wp-file-upload plugin, meaning that numerous WordPress installations could be vulnerable simultaneously. According to ATT&CK framework, this vulnerability maps to T1190 (Exploit Public-Facing Application) and T1059 (Command and Scripting Interpreter) techniques, as it allows for exploitation of publicly accessible web applications and execution of malicious code through scripting interpreters.
Mitigation strategies for this vulnerability require immediate action to upgrade the wp-file-upload plugin to version 2.5.0 or later, which contains proper file validation and restriction mechanisms. Organizations should implement comprehensive file upload restrictions that validate file content, not just extensions, and employ additional security layers such as web application firewalls to monitor and block suspicious upload attempts. The remediation process should include thorough security auditing of all installed plugins to identify similar vulnerabilities, as this issue represents a common pattern in plugin development where security considerations are often overlooked. Regular security assessments and vulnerability scanning should be implemented to detect such issues before they can be exploited. Additionally, administrators should enforce strict file permissions and implement proper input sanitization practices across all web applications. The vulnerability also highlights the importance of keeping all WordPress components updated and following security best practices such as implementing least privilege access controls and monitoring for unauthorized file modifications. Organizations should consider implementing automated patch management systems to ensure timely updates of all software components, including third-party plugins that may introduce similar security weaknesses.