External risk intelligence

D-Link DWR-M961 Command Execution via Buffer Overflow

CVE advisorySeverity: CRITICAL (CVSS 9.3)

CVE-2026-71958

The vulnerability exists in the quicksetup.cgi interface of a router. Routers and their management interfaces are commonly exposed to the internet or reachable via the WAN interface by design to facilitate remote configuration and access, making them a standard example of a public-facing network appliance.

Buffer Overflow

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

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This advisory concerns a critical vulnerability found in D-Link DWR-M961 devices. The flaw, located in the quicksetup.cgi interface, allows for arbitrary command execution or device crashes through a buffer overflow. This could potentially impact devices that are directly accessible from the internet.

Flaw in router's setup interface.
Affects remote access and commands.
Confirm relevance and exposure.

Attack Path

How an attacker could exploit the issue

An attacker could remotely access a vulnerable device and exploit a buffer overflow flaw within the quicksetup.cgi interface. By sending crafted input to specific fields, they could execute arbitrary commands or cause the device to malfunction.

Device accessible via the network.
Crafting overly long strings to specific fields.
Arbitrary command execution or denial of service.

Live Threat

Current exploitation, exposure, and threat context

A buffer overflow in the quicksetup.cgi interface of D-Link DWR-M961 devices could allow a remote attacker to execute arbitrary commands or cause the device to crash when supported by the advisory.

Device commands and configuration.
Malformed HTTP requests to the interface.
Device disruption or unauthorized control.

Operational Fix

Recommended remediation, mitigation, and detection steps

The D-Link DWR-M961 router's quicksetup.cgi interface is vulnerable to remote command execution and denial-of-service attacks. Given that this is a network-facing device, the Network/Security team or Infrastructure team should lead the initial triage. The first practical step is to identify all deployed DWR-M961 devices, assess their exposure (especially WAN-facing interfaces), confirm business criticality, and then coordinate remediation with the vendor and any relevant asset owners.

Network/Security team owns the issue.
Verify WAN-facing device exposure and criticality.
Coordinate vendor engagement and remediation planning.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the D-Link DWR-M961?

The D-Link DWR-M961 is a 4G LTE router designed to provide wireless internet connectivity. It functions as a gateway for local networks, managing traffic and device configuration through a built-in web-based management interface.

What does CVE-2026-71958 mean?

This vulnerability is a buffer overflow, specifically classified as CWE-120. It occurs when a program tries to store more data in a memory buffer than it can hold. In this case, the device's management interface fails to properly check the length of data provided by a user, which can lead to unexpected behavior like system crashes or unauthorized command execution.

How is this vulnerability triggered?

An attacker triggers this by sending malformed, overly long strings to the 'test4', 'ssid2', or 'username' fields within the quicksetup.cgi interface. Simply visiting the device's main landing page or using standard, correctly formatted configuration settings will not trigger the overflow; it requires intentional submission of excessively long input designed to exceed the buffer's capacity.

Is my device at risk?

Halo Surface Signal indicates this risk is higher for devices with management interfaces reachable via the internet or the WAN interface. Because this is a router-level management interface, any DWR-M961 configured to allow remote access from outside the local network is more likely to be reachable by external actors attempting to exploit this vulnerability.

What should I do if I use this router?

Begin by creating an inventory of all DWR-M961 units in your environment. Prioritize identifying devices that are currently accessible from the internet and restrict access to their management interfaces immediately. Follow up by checking the official D-Link support channels for any available updates or specific security guidance to address this configuration risk.

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.