CVE-2018-15137 in CLR-M20
Summary
by MITRE
CeLa Link CLR-M20 devices allow unauthorized users to upload any file (e.g., asp, aspx, cfm, html, jhtml, jsp, or shtml), which causes remote code execution as well. Because of the WebDAV feature, it is possible to upload arbitrary files by utilizing the PUT method.
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Analysis
by VulDB Data Team • 08/20/2024
The CVE-2018-15137 vulnerability affects CeLa Link CLR-M20 devices and represents a critical security flaw that enables unauthorized remote code execution through arbitrary file upload capabilities. This vulnerability specifically leverages the WebDAV functionality present in these network devices, creating a pathway for attackers to exploit the system by uploading malicious files via the PUT method. The affected device family operates as network infrastructure equipment that typically serves as a gateway or communication endpoint, making it a prime target for attackers seeking persistent access to network environments. The vulnerability exists due to insufficient input validation and access control mechanisms within the device's web interface, allowing any authenticated or unauthenticated user to bypass normal file upload restrictions. This flaw directly violates security principles outlined in the OWASP Top Ten, particularly the category of "Insecure File Upload" which is classified as CWE-434, and represents a significant weakness in the device's authorization model that enables privilege escalation through file manipulation. The WebDAV implementation lacks proper sanitization of file extensions and content type validation, creating a dangerous attack surface where attackers can upload web shells or other malicious executables that can be executed within the device's operating environment.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass complete system compromise and potential network infiltration. Attackers can upload various file types including asp, aspx, cfm, html, jhtml, jsp, and shtml files, with the most dangerous implications arising from the ability to upload server-side include files or web shells that can execute arbitrary commands with the privileges of the web server process. The PUT method implementation in WebDAV allows for direct file creation and modification within the web root directory, effectively giving attackers the ability to establish persistent backdoors or deploy malware directly onto the device. This vulnerability creates a pathway for attackers to escalate privileges and potentially use the compromised device as a pivot point for attacking other systems within the local network. The attack vector is particularly concerning because it requires minimal authentication, often allowing unauthenticated exploitation, and the uploaded files can be executed immediately upon access, providing attackers with immediate control over the device's functions. From an ATT&CK framework perspective, this vulnerability maps to T1190 (Exploit Public-Facing Application) and T1059 (Command and Scripting Interpreter) with potential for T1078 (Valid Accounts) and T1566 (Phishing) if attackers use the compromised device to launch further attacks.
Mitigation strategies for CVE-2018-15137 should focus on immediate network segmentation and access control measures to prevent unauthorized access to the affected devices. Organizations must implement strict file type validation and content filtering mechanisms that prevent upload of executable or potentially dangerous file extensions, while also disabling unnecessary WebDAV functionality where possible. The recommended approach includes applying manufacturer-provided firmware updates or patches that address the file upload validation flaws, implementing network monitoring to detect suspicious file upload activities, and configuring access controls to restrict WebDAV operations to authorized administrators only. Security teams should also deploy intrusion detection systems that can identify and alert on PUT method usage patterns and anomalous file upload behaviors. From a compliance standpoint, this vulnerability directly impacts PCI DSS requirements for secure configuration and network monitoring, requiring organizations to maintain updated device firmware and implement proper access controls. The vulnerability also highlights the importance of secure coding practices and input validation, as outlined in the CWE guidelines for preventing file upload vulnerabilities, which emphasize the need for strict file extension checking, content type verification, and proper access controls to prevent unauthorized file operations. Organizations should conduct comprehensive vulnerability assessments of all network devices to identify similar weaknesses in other infrastructure equipment and implement robust network segmentation to limit the potential impact of such attacks.