CVE-2018-18874 in nc-cms
Summary
by MITRE
nc-cms through 2017-03-10 allows remote attackers to execute arbitrary PHP code via the "Upload File or Image" feature, with a .php filename and "Content-Type: application/octet-stream" to the index.php?action=file_manager_upload URI.
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Analysis
by VulDB Data Team • 06/04/2023
The vulnerability identified as CVE-2018-18874 affects nc-cms version 2017-03-10 and earlier, representing a critical remote code execution flaw that enables attackers to execute arbitrary PHP code on vulnerable systems. This vulnerability resides within the file upload functionality of the content management system, specifically targeting the index.php?action=file_manager_upload endpoint. The flaw demonstrates a classic improper input validation issue that allows malicious users to bypass security restrictions and upload malicious files with PHP extensions.
The technical exploitation of this vulnerability leverages a combination of file extension manipulation and content-type header manipulation to circumvent upload restrictions. Attackers can upload files with .php extensions while setting the Content-Type header to application/octet-stream, effectively bypassing the CMS's file type validation mechanisms. This technique exploits a weakness in the file validation logic where the system relies on Content-Type headers rather than implementing robust file type verification based on actual file content. The vulnerability aligns with CWE-434 which describes improper restriction of uploads of executable files, and represents a clear example of insecure file upload handling that has been frequently exploited in web applications.
The operational impact of this vulnerability is severe as it provides remote attackers with complete control over the affected system. Successful exploitation allows attackers to execute arbitrary PHP code, which can lead to full system compromise, data exfiltration, and potential lateral movement within network environments. The vulnerability can be exploited remotely without authentication, making it particularly dangerous as it requires no prior access to the system. This type of vulnerability falls under the ATT&CK technique T1190 for Exploit Public-Facing Application, and represents a common vector for initial access and persistence in targeted attacks.
Mitigation strategies for this vulnerability include immediate patching of the nc-cms to the latest version that addresses the file upload validation issue. Organizations should implement strict file type validation that examines actual file content rather than relying solely on Content-Type headers or file extensions. Additional protective measures include implementing proper file upload restrictions such as storing uploaded files outside the web root directory, implementing content validation checks, and employing web application firewalls to monitor and block suspicious upload attempts. The vulnerability also highlights the importance of following secure coding practices and implementing proper input validation as outlined in OWASP Top Ten security guidelines, specifically addressing the prevention of file upload attacks and ensuring proper file handling procedures are in place to prevent similar issues from occurring in other applications.