DrayTek VigorSwitch tftp_upgrade filename command injection

Summaryinfo

A vulnerability was found in DrayTek VigorSwitch and classified as very critical. Impacted is the function tftp_upgrade. Executing a manipulation of the argument filename can lead to command injection. This vulnerability is tracked as CVE-2026-71931. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability has been found in DrayTek VigorSwitch (the affected version is unknown) and classified as very critical. This vulnerability affects the function tftp_upgrade. The manipulation of the argument filename with an unknown input leads to a command injection vulnerability. The CWE definition for the vulnerability is CWE-77. The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Multiple DrayTek VigorSwitch models contain a command injection vulnerability in the tftp_upgrade function. The vulnerability is caused by insufficient filtering before the filename field is concatenated into a command. 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.

The advisory is available at draytek.com. This vulnerability was named CVE-2026-71931 since 08/08/2026. The exploitation appears to be easy. The attack can be initiated remotely. Additional levels of successful authentication are required for exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 08/24/2026). This vulnerability is assigned to T1202 by the MITRE ATT&CK project.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

• Router Operating System

Vendor

• DrayTek

Name

• VigorSwitch

License

• commercial

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

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Entryinfo

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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