CVE-2021-20123 in VigorConnect
Summary
by MITRE • 10/13/2021
A local file inclusion vulnerability exists in Draytek VigorConnect 1.6.0-B3 in the file download functionality of the DownloadFileServlet endpoint. An unauthenticated attacker could leverage this vulnerability to download arbitrary files from the underlying operating system with root privileges.
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Analysis
by VulDB Data Team • 09/30/2024
The vulnerability identified as CVE-2021-20123 represents a critical local file inclusion flaw within Draytek VigorConnect version 1.6.0-B3, specifically affecting the DownloadFileServlet endpoint. This issue stems from inadequate input validation and sanitization mechanisms that fail to properly restrict file path traversal attempts. The vulnerability allows unauthenticated attackers to exploit the file download functionality and retrieve arbitrary files from the underlying operating system. The attack vector leverages the absence of proper access controls and path validation, enabling remote exploitation without requiring prior authentication credentials. Security researchers have identified that this vulnerability exists due to insufficient restrictions on user-supplied file paths, which permits attackers to manipulate the file download process to access sensitive system files.
The technical exploitation of this vulnerability occurs through the DownloadFileServlet endpoint where user input is directly incorporated into file system operations without adequate sanitization. This flaw falls under the Common Weakness Enumeration category CWE-22, which specifically addresses improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The vulnerability allows attackers to craft malicious requests that bypass normal file access controls and retrieve files that should remain inaccessible to unauthorized users. When an attacker submits a crafted file path parameter to the DownloadFileServlet, the application processes the request without validating whether the specified file path is within the intended download directory, enabling access to system files, configuration data, and potentially sensitive information stored in restricted locations.
The operational impact of CVE-2021-20123 is severe and far-reaching for organizations utilizing vulnerable Draytek VigorConnect appliances. An unauthenticated attacker with access to the network can exploit this vulnerability to obtain critical system information, including configuration files, user credentials, system logs, and other sensitive data that could be used for further compromise. The vulnerability's ability to operate with root privileges means that attackers can access files that are typically protected by system-level access controls, potentially leading to complete system compromise. This threat is particularly concerning because it affects network infrastructure devices that often serve as gateways between internal networks and external environments, making them prime targets for attackers seeking to establish persistent access or escalate privileges within corporate networks. The vulnerability's exploitation does not require authentication, which significantly increases the attack surface and reduces the barriers for potential attackers.
Organizations should immediately implement mitigation strategies to address this vulnerability, beginning with applying the latest firmware updates provided by Draytek to patch the vulnerable DownloadFileServlet endpoint. Network segmentation and access control measures should be enforced to limit exposure of the vulnerable appliance to untrusted networks, while implementing network monitoring to detect suspicious file download activities. The implementation of proper input validation and sanitization controls at the application level can help prevent path traversal attempts, and organizations should consider deploying web application firewalls to filter malicious requests targeting the vulnerable endpoint. Security teams should conduct thorough vulnerability assessments to identify any additional systems running vulnerable versions of VigorConnect software and ensure that all network devices are properly configured with appropriate access controls and network segmentation measures to minimize the potential impact of successful exploitation attempts.