CVE-2017-18048 in Monstra
Summary
by MITRE
Monstra CMS 3.0.4 allows users to upload arbitrary files, which leads to remote command execution on the server, for example because .php (lowercase) is blocked but .PHP (uppercase) is not.
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Analysis
by VulDB Data Team • 06/25/2024
The vulnerability identified as CVE-2017-18048 represents a critical file upload restriction bypass in Monstra CMS version 3.0.4 that enables attackers to execute arbitrary commands on the affected server. This flaw stems from an incomplete file type validation mechanism that fails to properly sanitize file extensions, creating a pathway for malicious actors to bypass security controls through case-sensitive file extension manipulation. The vulnerability is particularly concerning because it demonstrates a fundamental flaw in the application's security architecture where the system relies on simple extension checking rather than comprehensive file content verification. The specific implementation issue occurs when the application blocks lowercase .php extensions while simultaneously allowing uppercase .PHP extensions to be uploaded, exploiting the inconsistency in validation logic to gain unauthorized access to server execution capabilities.
The technical exploitation of this vulnerability follows a well-established pattern that aligns with CWE-434, which addresses insecure file upload vulnerabilities. Attackers can leverage this weakness by uploading a file with a .PHP extension in uppercase letters, thereby circumventing the restrictive file upload filters. Once successfully uploaded, the malicious file can be executed by the web server, providing attackers with remote command execution capabilities. This allows them to perform various malicious activities including but not limited to data exfiltration, server compromise, and establishment of persistent access points. The vulnerability operates at the intersection of multiple attack vectors defined in the MITRE ATT&CK framework under T1190 for Exploit Public-Facing Application and T1059 for Command and Scripting Interpreter, demonstrating how a seemingly minor validation flaw can enable comprehensive system compromise.
The operational impact of CVE-2017-18048 extends beyond immediate exploitation to encompass long-term security implications for affected organizations. Server compromise through this vulnerability can result in complete system takeover, data breaches, and potential lateral movement within network environments. The vulnerability affects the integrity and confidentiality of the entire CMS deployment, as attackers can modify existing files, inject malicious code, or establish backdoors for continued access. Organizations running Monstra CMS 3.0.4 are particularly vulnerable because the flaw exists in the core file upload functionality that is essential for content management operations, making it difficult to implement effective workarounds without complete system patching.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term architectural improvements. The primary solution involves applying the official patch or upgrading to a version of Monstra CMS that properly implements file type validation, ensuring that all variations of potentially dangerous extensions are blocked regardless of case sensitivity. Organizations should implement comprehensive file validation mechanisms that examine both file extensions and content signatures rather than relying solely on extension filtering. Additional protective measures include restricting upload permissions to specific user roles, implementing proper file type whitelisting, and configuring web server rules to prevent execution of uploaded files in web-accessible directories. Security monitoring should include detection of unusual file upload patterns and regular vulnerability scanning to identify similar weaknesses in other applications within the organization's infrastructure, aligning with security best practices outlined in NIST SP 800-53 and ISO 27001 standards for secure application development and deployment.