CVE-2015-2194 in Fusion
Summary
by MITRE
Unrestricted file upload vulnerability in the fusion_options function in functions.php in the Fusion theme 3.1 for Wordpress allows remote authenticated users to execute arbitrary code by uploading a file with an executable extension in a fusion_save action, then accessing it via unspecified vectors.
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Analysis
by VulDB Data Team • 04/14/2018
The vulnerability described in CVE-2015-2194 represents a critical security flaw within the Fusion theme version 3.1 for WordPress platforms. This issue stems from an unrestricted file upload functionality that operates through the fusion_options function located in the functions.php file of the affected theme. The vulnerability specifically targets the fusion_save action mechanism, which creates an avenue for malicious actors to bypass normal file validation processes and upload potentially harmful files to the target system.
The technical implementation of this vulnerability allows authenticated users to exploit a design flaw in the file upload validation logic. When users with valid credentials attempt to save theme options through the fusion_save action, the system fails to properly validate file extensions or content types. This oversight enables attackers to upload files with executable extensions such as .php, .asp, or .jsp, which can then be executed on the web server. The vulnerability is particularly dangerous because it leverages legitimate administrative functions within the WordPress theme system, making detection more challenging and exploitation more plausible.
The operational impact of this vulnerability extends beyond simple code execution capabilities. Attackers who successfully exploit this flaw can gain full control over the compromised WordPress installation, potentially leading to complete system compromise. The unspecified vectors mentioned in the description suggest that once a malicious file is uploaded, multiple access methods may be available to execute the payload, including direct web access, server-side inclusion, or integration with other attack vectors. This broad attack surface increases the severity and potential damage of the compromise.
From a cybersecurity perspective, this vulnerability aligns with CWE-434, which addresses the improper restriction of uploads of executable code, and maps to several ATT&CK techniques including T1059 for executing malicious code and T1078 for valid accounts usage. The vulnerability demonstrates poor input validation and inadequate file type checking mechanisms that are common in web application security flaws. Organizations using the affected Fusion theme version 3.1 should immediately implement mitigations including updating to patched versions, implementing strict file extension validation, disabling unnecessary file upload capabilities, and monitoring for suspicious file uploads. Additionally, network segmentation and web application firewalls can provide additional layers of protection against exploitation attempts.
The broader implications of this vulnerability highlight the critical importance of proper file upload validation in web applications. WordPress themes and plugins that fail to implement robust security measures for file handling create dangerous attack surfaces that can be exploited by threat actors. Security practitioners should conduct comprehensive audits of all theme and plugin code to identify similar validation flaws and ensure that all file upload mechanisms properly validate both file extensions and content types before allowing uploads to proceed. Regular security updates and patch management processes become essential defensive measures against such vulnerabilities.