CVE-2015-9479 in ACF-Frontend-Display Plugin
Summary
by MITRE
The ACF-Frontend-Display plugin through 2015-07-03 for WordPress has arbitrary file upload via an action=upload request to js/blueimp-jQuery-File-Upload-d45deb1/server/php/index.php.
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Analysis
by VulDB Data Team • 01/07/2024
The vulnerability identified as CVE-2015-9479 affects the ACF-Frontend-Display plugin for WordPress, specifically versions through 2015-07-03, presenting a critical arbitrary file upload flaw that enables remote attackers to execute malicious code on affected systems. This vulnerability resides within the plugin's file upload functionality, where the action=upload parameter in the js/blueimp-jQuery-File-Upload-d45deb1/server/php/index.php endpoint fails to properly validate file types or implement adequate access controls. The flaw allows unauthorized users to bypass normal file upload restrictions and potentially upload malicious files such as web shells or malware, which can then be executed on the target server. The vulnerability directly maps to CWE-434, which describes insecure file upload vulnerabilities where applications accept files without proper validation, and aligns with ATT&CK technique T1190, which covers exploiting vulnerabilities in web applications to gain unauthorized access. This arbitrary file upload vulnerability represents a severe threat to WordPress installations as it provides attackers with a direct pathway to compromise the entire web server environment.
The technical implementation of this vulnerability stems from insufficient input validation and access control mechanisms within the plugin's file handling code. When users submit files through the upload interface, the system does not adequately verify the file extension, MIME type, or file content before storing the uploaded files on the server. The action=upload parameter in the specified PHP endpoint lacks proper authentication checks, allowing any remote attacker to directly access the file upload functionality without proper authorization. This flaw typically occurs when developers fail to implement proper file type filtering, directory traversal protection, or upload directory permissions checks. The vulnerability exists because the plugin does not enforce strict validation of uploaded files, nor does it implement secure file storage practices such as storing uploaded files outside the web root or renaming files to prevent execution. Attackers can exploit this by crafting malicious requests that bypass normal upload restrictions, potentially leading to complete system compromise through the execution of uploaded malicious code.
The operational impact of CVE-2015-9479 extends far beyond simple unauthorized file uploads, as it provides attackers with persistent access to compromised WordPress installations and potentially the entire underlying server infrastructure. Once an attacker successfully uploads malicious files, they can establish backdoors, deploy additional malware, or use the compromised system as a launchpad for further attacks against internal networks. The vulnerability affects not only the WordPress site but also poses risks to the entire hosting environment, as compromised web servers often have elevated privileges that can be leveraged for privilege escalation attacks. Additionally, the compromised site becomes a potential vector for distributing malware to visitors, conducting phishing attacks, or using the system for botnet activities. The vulnerability's exploitation can result in data breaches, defacement of websites, unauthorized access to sensitive information, and complete system compromise. Organizations may face regulatory compliance violations, financial losses, reputational damage, and potential legal consequences due to the unauthorized access and data exposure that results from such vulnerabilities.
Mitigation strategies for CVE-2015-9479 require immediate action to address the root cause of the vulnerability through multiple layers of security controls. The primary remediation involves updating the ACF-Frontend-Display plugin to a version that properly validates file uploads and implements secure file handling practices, as the vulnerability was resolved in subsequent releases. Organizations should also implement strict file type validation by checking file extensions against a whitelist of allowed types, implementing proper MIME type verification, and ensuring uploaded files are stored in directories outside the web root. Network-level protections include implementing web application firewalls that can detect and block malicious file upload attempts, configuring proper access controls to restrict upload functionality to authenticated users only, and monitoring upload directories for suspicious activity. Security measures should also include regular security audits of WordPress plugins, implementing proper file permissions on upload directories, and establishing automated scanning processes to detect compromised files. The vulnerability's remediation aligns with security best practices outlined in the OWASP Top Ten and follows the principle of least privilege, ensuring that only authorized users can access file upload functionality while maintaining proper input validation and output encoding throughout the application. Additionally, organizations should conduct regular vulnerability assessments and penetration testing to identify similar security flaws in other web applications and plugins that may be susceptible to similar arbitrary file upload attacks.