CVE-2018-15601 in Elefant
Summary
by MITRE
apps/filemanager/handlers/upload/drop.php in Elefant CMS 2.0.3 performs a urldecode step too late in the "Cannot upload executable files" protection mechanism.
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Analysis
by VulDB Data Team • 05/04/2023
The vulnerability identified as CVE-2018-15601 resides within the Elefant CMS 2.0.3 file upload handler located at apps/filemanager/handlers/upload/drop.php. This flaw represents a critical security oversight in the content management system's file upload protection mechanisms, specifically affecting the validation process for executable file uploads. The vulnerability stems from a timing issue in the security check implementation where the URL decoding operation occurs at an inappropriate stage in the upload processing pipeline, creating a window of opportunity for malicious actors to bypass intended security controls.
The technical flaw manifests when the system attempts to prevent upload of executable files through its protection mechanism. The system performs a URL decoding operation at a point in the code execution flow that is too late in the process, allowing attackers to craft specially encoded filenames that initially pass validation checks. This late-stage decoding means that malicious payloads can be embedded in the filename using URL encoding techniques, which then get decoded after the security validation has already been completed. The vulnerability essentially undermines the intended security posture by allowing attackers to circumvent the protection mechanism that should prevent execution of potentially harmful files.
From an operational impact perspective, this vulnerability creates significant risks for Elefant CMS installations, particularly in environments where users can upload files or where the system handles user-generated content. Attackers can exploit this weakness to upload malicious files that would otherwise be blocked by the security mechanism, potentially leading to remote code execution, server compromise, or other malicious activities. The vulnerability is particularly concerning because it affects the core file management functionality of the CMS, making it a prime target for exploitation in broader attack campaigns. This flaw essentially allows attackers to bypass a fundamental security control designed to protect against executable file uploads, which can result in complete system compromise.
Security professionals should consider this vulnerability in the context of CWE-502 which addresses deserialization of untrusted data, and potentially CWE-20 which covers input validation issues. The flaw also aligns with ATT&CK technique T1190 for exploitation of remote services, particularly in the context of web application attacks. Organizations should prioritize immediate patching of this vulnerability through the official Elefant CMS update channels. Additional mitigations include implementing strict file type validation at multiple stages of the upload process, deploying web application firewalls to monitor for suspicious upload patterns, and conducting thorough security assessments of the file management system components. Regular security audits of CMS components and validation of security controls should be implemented to prevent similar timing-based vulnerabilities in the future.