CVE-2026-71921 in VigorSwitch
Summary
by MITRE • 08/24/2026
Multiple DrayTek VigorSwitch models contain a pre-authentication command injection vulnerability in the setget.cgi interface. The vulnerability is caused by insufficient filtering of the pass field before command execution. A remote attacker can trigger this vulnerability via crafted input to execute arbitrary commands with root privileges.
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Analysis
by VulDB Data Team • 08/24/2026
The identified security flaw resides within the web management interface of multiple DrayTek VigorSwitch models, specifically affecting the setget.cgi endpoint. This component is responsible for handling configuration changes and system settings through HTTP requests. The vulnerability stems from a critical implementation error where input validation mechanisms are insufficiently rigorous when processing data submitted to this specific CGI script. In particular, the pass field, which typically handles authentication credentials or password-related parameters, fails to properly sanitize user-supplied input before it is passed to underlying shell commands for execution. This lack of proper filtering allows special characters and command separators to be interpreted by the operating system's command interpreter rather than being treated as literal data strings.
From a technical perspective, this constitutes a classic pre-authentication command injection vulnerability. Because the flaw exists in an endpoint that does not require prior authentication, any remote actor on the network can exploit it without needing valid credentials. By crafting specific HTTP requests containing malicious payloads within the pass field, an attacker can inject arbitrary shell commands. These injected commands are executed with root privileges because the CGI script typically runs under a high-privilege context to facilitate administrative changes. This effectively grants the attacker full control over the affected device's operating system, allowing them to read sensitive configuration files, modify network settings, install persistent backdoors, or pivot into other parts of the internal network infrastructure.
The operational impact of this vulnerability is severe due to its remote and unauthenticated nature. Attackers can compromise the integrity, confidentiality, and availability of the managed switch. Once root access is achieved, the device can be used as a foothold for lateral movement within the local area network. This could lead to broader network compromises, including interception of traffic, disruption of critical services, or use of the compromised hardware in botnets. The ease of exploitation means that automated scanning tools and opportunistic attackers can rapidly identify and exploit vulnerable devices across large networks with minimal effort.
This vulnerability aligns closely with Common Weakness Enumeration (CWE) identifiers such as CWE-78 Improper Neutralization of Special Elements used in an OS Command, commonly known as OS Command Injection, and CWE-287 Improvement of Authentication Bypass or Evasion. In terms of the MITRE ATT&CK framework, this exploitation technique maps to T1059 Command and Scripting Interpreter, specifically leveraging shell commands for unauthorized access. The pre-authentication aspect also relates to techniques involving unauthenticated access to administrative interfaces.
Mitigation strategies should prioritize immediate patching if a vendor-provided firmware update is available that addresses the input validation in setget.cgi. In cases where patches are not yet released or applicable, network-level controls can provide temporary relief. Implementing strict firewall rules to restrict access to the management interface of these switches solely from trusted administrative subnets can significantly reduce the attack surface. Additionally, disabling unnecessary web services on devices that do not require remote configuration capabilities is a recommended best practice. Organizations should also conduct regular vulnerability assessments and penetration testing focused on network infrastructure components to detect such misconfigurations or unpatched flaws before they are exploited by malicious actors.