CVE-2026-2959: D-Link DWR-M960 Buffer Overflow Vulnerability

CVE-2026-2959 Overview

A stack-based buffer overflow vulnerability has been identified in D-Link DWR-M960 firmware version 1.01.07. This vulnerability affects the function sub_44E0F8 within the file /boafrm/formNewSchedule. When the url argument is manipulated, it triggers a stack-based buffer overflow condition that can be exploited remotely by authenticated attackers.

The vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), a category of memory corruption flaws that can lead to arbitrary code execution, denial of service, or complete device compromise. Given that the exploit is publicly available, organizations using affected D-Link routers should prioritize remediation efforts.

Critical Impact

Remote attackers with low-level privileges can exploit this stack-based buffer overflow to potentially execute arbitrary code on affected D-Link DWR-M960 devices, leading to full device compromise and network infiltration.

Affected Products

• D-Link DWR-M960 Firmware version 1.01.07
• D-Link DWR-M960 Hardware revision B1
• dlink dwr-m960_firmware

Discovery Timeline

• 2026-02-23 - CVE-2026-2959 published to NVD
• 2026-02-23 - Last updated in NVD database

Technical Details for CVE-2026-2959

Vulnerability Analysis

This vulnerability exists within the web management interface of the D-Link DWR-M960 router. The affected function sub_44E0F8 in the /boafrm/formNewSchedule endpoint fails to properly validate the length of user-supplied input in the url parameter before copying it into a fixed-size stack buffer.

When an attacker sends a crafted HTTP request with an oversized url parameter value, the application copies the malicious input without bounds checking, causing data to overflow beyond the allocated stack buffer. This overflow can overwrite adjacent memory on the stack, including the saved return address, potentially allowing an attacker to redirect execution flow to attacker-controlled code.

The network-accessible nature of this vulnerability combined with low attack complexity makes it particularly dangerous for devices exposed to untrusted networks. While authentication is required (low privileges), many router deployments use default or weak credentials, increasing the practical exploitability of this flaw.

Root Cause

The root cause of this vulnerability is improper input validation in the sub_44E0F8 function. The code fails to verify that the length of the url argument does not exceed the allocated buffer size on the stack before performing the copy operation. This is a classic instance of missing boundary checks that leads to memory corruption.

The /boafrm/formNewSchedule endpoint processes schedule configuration data submitted through the router's web interface. The vulnerable function does not employ safe string handling functions or length validation, allowing attackers to control the amount of data written to the stack.

Attack Vector

The attack can be executed remotely over the network. An authenticated attacker can send a specially crafted HTTP POST request to the /boafrm/formNewSchedule endpoint with a malicious url parameter. The oversized input triggers the stack-based buffer overflow, potentially leading to:

1. Denial of Service: Crashing the web server or entire device by corrupting critical stack data
2. Remote Code Execution: Overwriting the return address to redirect execution to shellcode
3. Device Compromise: Gaining persistent access to the router's operating system

The vulnerability mechanism involves sending an HTTP request to the vulnerable endpoint with a manipulated url parameter that exceeds expected buffer bounds. When processed by sub_44E0F8, the oversized data overwrites adjacent stack memory. Technical details and proof-of-concept information are available in the GitHub Issue Discussion.

Detection Methods for CVE-2026-2959

Indicators of Compromise

• Unusual HTTP POST requests to /boafrm/formNewSchedule containing abnormally long url parameter values
• Router crashes, reboots, or unresponsive web management interface following suspicious network activity
• Unexpected firmware modifications or configuration changes on D-Link DWR-M960 devices
• Network traffic anomalies originating from the router to unknown external destinations

Detection Strategies

• Implement network intrusion detection rules to identify HTTP requests with oversized parameters targeting /boafrm/formNewSchedule
• Monitor D-Link DWR-M960 devices for unexpected reboots or service interruptions that may indicate exploitation attempts
• Deploy web application firewall rules to block requests with excessively long URL parameters to router management interfaces
• Review router access logs for unusual authentication patterns or repeated requests to the vulnerable endpoint

Monitoring Recommendations

• Enable logging on D-Link DWR-M960 devices and forward logs to a centralized SIEM for correlation analysis
• Implement network segmentation to isolate router management interfaces from untrusted networks
• Configure alerts for abnormal traffic patterns targeting router administrative endpoints
• Regularly review device configurations for unauthorized changes that may indicate successful exploitation

How to Mitigate CVE-2026-2959

Immediate Actions Required

• Restrict access to the D-Link DWR-M960 web management interface to trusted IP addresses only
• Disable remote management access if not required for operations
• Change default credentials and implement strong authentication on all D-Link devices
• Consider network segmentation to limit exposure of vulnerable devices
• Monitor for firmware updates from D-Link addressing this vulnerability

Patch Information

At the time of publication, no official patch has been released by D-Link for this vulnerability. Organizations should monitor the D-Link Security Resources page for security advisories and firmware updates. Additional technical details are available through VulDB #347326.

Workarounds

• Implement access control lists (ACLs) to restrict access to the router's web interface from trusted management networks only
• Deploy a web application firewall or reverse proxy in front of the management interface to filter malicious requests
• Disable the web management interface entirely and manage the device through alternative methods if available
• Consider replacing vulnerable devices with supported hardware that receives regular security updates

# Example: Restrict management interface access using firewall rules
# Block external access to router management port (example iptables rules)
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP