CVE-2026-71923 in VigorSwitch G2540xs
Summary
by MITRE • 08/24/2026
Multiple DrayTek VigorSwitch models contain a command injection vulnerability in the auth_set function. The vulnerability is caused by insufficient filtering of the username and password fields before command execution. A remote attacker can trigger this vulnerability via crafted input to execute arbitrary commands with root privileges. Exploitation requires valid administrative credentials for the device's web management interface.
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Analysis
by VulDB Data Team • 08/24/2026
The identified security flaw resides within the authentication handling mechanism, specifically the auth_set function, of multiple DrayTek VigorSwitch models. This component is responsible for processing user input during the credential update or verification process on the device’s web-based management interface. The core technical deficiency lies in the insufficient sanitization and validation of data entered into the username and password fields before these values are passed to underlying system commands. Instead of strictly validating that inputs conform to expected alphanumeric patterns or length constraints, the application fails to adequately escape special characters such as semicolons, ampersands, or backticks. This lack of rigorous input filtering allows an attacker to inject malicious shell metacharacters directly into the command execution pipeline.
From a technical perspective, this vulnerability is classified under CWE-78 Improper Neutralization of Special Elements used in an OS Command, commonly known as Operating System Command Injection. The flaw enables a remote code execution scenario where user-supplied data is interpreted not just as string parameters but as executable instructions by the operating system shell. Because the vulnerable function operates with elevated privileges to manage network device configurations, any command injected through this vector inherits these high-level permissions. Consequently, an attacker who successfully exploits this weakness can execute arbitrary commands on the underlying Linux-based firmware of the switch with root access, effectively gaining full control over the hardware.
The operational impact of this vulnerability is severe due to its potential for complete system compromise. Although exploitation requires valid administrative credentials for the web management interface, which acts as a prerequisite authentication barrier, the presence of such credentials often indicates that an attacker has already breached perimeter defenses or obtained stolen login data through phishing or credential stuffing attacks. Once authenticated, the ability to execute arbitrary commands allows the adversary to modify network configurations, install persistent backdoors, exfiltrate sensitive traffic data, or pivot into other segments of the internal network. This transforms a simple authentication bypass scenario into a critical infrastructure compromise, potentially disrupting business operations and violating compliance requirements related to network security controls.
In terms of threat modeling, this vulnerability aligns with MITRE ATT&CK techniques involving Command and Scripting Interpreter abuse (T1059) and Remote Services such as SSH or Web Interface exploitation (T1210). The attack path typically involves the adversary first gaining initial access through compromised administrative credentials, followed by leveraging the command injection flaw to establish persistence or escalate privileges further if necessary. Given that the vulnerability is in a network device management interface, it poses a significant risk for lateral movement within enterprise environments where managed switches are critical nodes for traffic segmentation and security policy enforcement.
Mitigation strategies must focus on both immediate remediation and long-term hardening of the authentication subsystem. The primary defense is to apply vendor-provided firmware updates that patch the auth_set function by implementing strict input validation, parameterized command execution, or secure API calls instead of direct shell invocation. Administrators should ensure that all DrayTek VigorSwitch models are updated to the latest stable release containing these security fixes. Additionally, organizations should enforce strong password policies and multi-factor authentication for administrative access to reduce the likelihood of credential compromise. Network segmentation strategies should also be reviewed to limit the blast radius in case a device is compromised, ensuring that management interfaces are not exposed directly to untrusted networks without additional protective controls such as web application firewalls or strict IP whitelisting.