External risk intelligence

D-Link Router Command Execution Vulnerability.

CVE advisoryKnown Exploit

CVE-2019-17621

The vulnerability affects consumer Wi-Fi routers and is triggered via UPnP requests within the local network. While consumer devices are sometimes exposed to the public internet, the UPnP service itself is intended for local network discovery and control, making direct public-internet exploitation less common without explicit misconfiguration or deliberate exposure.

OS Command Injection

Dlink Dir 859 Firmware

1.05b03 and earlier1.06b012.03b01 and earlier3.12b04 and earlier1.00b06 and earlier1.00b061.07b01 and earlier1.12b04 and earlier2.05b02 and earlier1.03b02 and earlier1.03b021....

Halo Surface Signal: 2 out of 5 — less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This vulnerability affects specific D-Link Wi-Fi router models. The flaw allows unauthenticated remote attackers to execute system commands with root privileges. This could lead to a complete compromise of the affected devices.

Vulnerable D-Link router models
Unauthenticated command execution
Complete device compromise

Attack Path

How an attacker could exploit the issue

An attacker can exploit a vulnerability in certain D-Link routers by sending a specially crafted HTTP request to the UPnP service. This action can allow an unauthenticated remote attacker to execute system commands with root privileges. The attack targets the UPnP endpoint URL /gena.cgi.

Unauthenticated network access is required.
Attacker sends a crafted HTTP SUBSCRIBE request.
Attacker gains root control.

Live Threat

Current exploitation, exposure, and threat context

A critical vulnerability exists in certain D-Link routers that allows an unauthenticated remote attacker to execute system commands with root privileges. This can be achieved by sending a specially crafted HTTP request to the router's UPnP service. The successful exploitation of this vulnerability could lead to a complete compromise of the affected device, impacting the confidentiality, integrity, and availability of systems and data connected to it. Given the severity, organizations should prioritize remediation.

Attackers need no special skill.
Exploitation occurs on the local network.
This warrants urgent attention.

Operational Fix

Recommended remediation, mitigation, and detection steps

This critical vulnerability allows unauthenticated remote attackers to execute system commands with root privileges on affected D-Link routers. The exploit targets the UPnP service via a specially crafted HTTP SUBSCRIBE request, posing a significant risk to the confidentiality, integrity, and availability of the affected systems and data. Organizations should prioritize addressing this vulnerability to mitigate potential business impact.

Identify exposed routers.
Isolate affected devices.
Apply vendor updates and verify.
Monitor for related activity.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is the D-Link DIR-859 Wi-Fi router and its purpose?

The D-Link DIR-859 is a Wi-Fi router designed to provide internet connectivity and establish a local network for numerous devices within a home or small office environment. It functions as a network gateway, connecting your devices to the internet and facilitating communication among them.

What type of weakness does CVE-2019-17621 represent?

CVE-2019-17621 is a command injection vulnerability, classified under CWE-78. This weakness enables an attacker to coerce the router into executing arbitrary operating system commands by submitting specially crafted input, deviating from the intended command execution.

How can an attacker exploit the UPnP service on affected D-Link routers?

An attacker can exploit this vulnerability by sending a specially crafted HTTP SUBSCRIBE request to the router's UPnP service. This targeted request exploits the UPnP endpoint URL, /gena.cgi, to achieve remote command execution as root.

What is the relevance of CVE-2019-17621 for network security?

This vulnerability is highly relevant as it allows unauthenticated remote attackers to execute system commands with root privileges on affected D-Link routers. Exploitation could lead to a complete compromise of the device and any data it handles, impacting confidentiality, integrity, and availability.

What actions should be taken to address this vulnerability?

To mitigate this risk, organizations should identify any exposed routers, isolate affected devices, and apply vendor-provided updates. It is also crucial to verify that updates have been successfully applied and to continuously monitor for any related malicious activity.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.