CVE-2026-71929 in VigorSwitch G2540xs
Summary
by MITRE • 08/24/2026
Multiple DrayTek VigorSwitch models contain a command injection vulnerability in the setDevProto 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 DrayTek VigorSwitch series, a line of managed network switches widely deployed in enterprise and small-to-medium business environments, contains a critical command injection vulnerability within its web-based management interface. This flaw resides specifically in the setDevProto function, which is responsible for configuring device protocol settings such as SNMP or RADIUS parameters. The root cause of this security issue lies in insufficient input validation and sanitization mechanisms applied to 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 escaping special shell characters, the application directly interpolates user-supplied data into command strings executed by the operating system with elevated privileges.
This architectural weakness allows a remote attacker who possesses valid administrative credentials for the device's web management interface to inject arbitrary operating system commands. By crafting specific HTTP requests that include malicious payloads within the username or password fields, an authenticated adversary can bypass intended functional boundaries and achieve code execution on the target switch. Because these switches often operate as critical infrastructure components managing network traffic segmentation and security policies, the ability to execute commands with root privileges represents a severe compromise of device integrity. The attacker gains full control over the underlying Linux-based firmware environment, enabling them to modify system configurations, install persistent backdoors, or pivot further into the internal network by leveraging the switch's position as an access point for other connected devices.
From a classification perspective, this vulnerability aligns with CWE-78 Improper Neutralization of Special Elements used in an OS Command commonly known as OS Command Injection. The exploitation scenario corresponds to ATT&CK technique T1059 Command and Scripting Interpreter, where the attacker utilizes built-in system utilities or interpreters to execute malicious commands. Furthermore, because the vulnerability requires prior authentication, it falls under the category of authenticated attacks, highlighting a failure in secure design principles regarding input handling even for privileged interfaces. The impact extends beyond simple device compromise; if an attacker gains root access, they can potentially exfiltrate sensitive network topology information, intercept unencrypted traffic passing through managed ports, or disrupt service availability by altering routing tables and VLAN configurations.
Mitigation strategies must prioritize immediate patching of the DrayTek VigorSwitch firmware to versions that address this specific input validation flaw in the setDevProto function. Organizations should verify their inventory for affected models and apply vendor-released updates as soon as they become available. In scenarios where patching is not immediately feasible, network segmentation controls should be enforced to restrict access to the management interfaces of these switches exclusively from trusted administrative subnets using strict firewall rules or VLAN isolation. Additionally, implementing multi-factor authentication for web-based management consoles can add a layer of defense against credential theft, although it does not directly mitigate the command injection flaw itself. Regular vulnerability scanning and penetration testing focused on authenticated attack vectors are recommended to identify similar input handling weaknesses in other network devices within the infrastructure.