CISA has added two DrayTek vulnerabilities, CVE-2021-20123 and CVE-2021-20124, to its Known Exploited Vulnerabilities (KEV) Catalog. These vulnerabilities affect DrayTek’s VigorConnect software, which is used to manage DrayTek network devices. Discovered by Tenable Research, the flaws allow attackers to execute unauthenticated local file inclusion and path traversal attacks, potentially exposing sensitive files with root privileges. Although patches have been available since October 2021, the vulnerabilities continue to be actively targeted by threat actors exploiting unpatched systems.
The vulnerabilities in question impact the DownloadFileServlet and WebServlet endpoints on DrayTek VigorConnect. By crafting specially designed requests using path traversal sequences, attackers can access files on the underlying operating system. Despite the availability of patches, the flaws are still being exploited due to the persistence of threat actors targeting systems with known vulnerabilities that have not been updated. This highlights the ongoing risk posed by unpatched vulnerabilities in widely used software.
While DrayTek devices are widespread, a smaller number of VigorConnect systems are exposed to the internet, making them particularly attractive targets for cybercriminals. Despite the relatively low number of affected assets, the simplicity of exploiting these vulnerabilities makes them enticing for attackers. Cybercriminals can leverage these flaws to gain unauthorized access to sensitive network configurations, enabling them to stay under the radar while infiltrating larger networks. This strategic targeting allows attackers to exploit systems with minimal complexity.
In response to the discovery, Tenable Research released proof-of-concept code for the vulnerabilities, which was made publicly available. DrayTek responded promptly by releasing an updated version of VigorConnect, version 1.6.1, in October 2021, addressing the vulnerabilities. However, given the rising number of attacks observed in 2024 and the continued exploitation of unpatched systems, it is crucial for users to update their devices promptly to avoid potential security breaches. Tenable’s vulnerability detection tools help identify affected systems, offering support for security teams in mitigating these risks.
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