CVE-2026-2881: D-Link DWR-M960 Buffer Overflow Flaw

CVE-2026-2881 Overview

A stack-based buffer overflow vulnerability has been identified in the D-Link DWR-M960 wireless router firmware version 1.01.07. This vulnerability exists in the sub_425FF8 function within the Advanced Firewall Configuration Endpoint (/boafrm/formFirewallAdv). Improper handling of the submit-url argument allows attackers to trigger a buffer overflow condition, potentially leading to remote code execution or denial of service.

Critical Impact

Authenticated remote attackers can exploit this stack-based buffer overflow to execute arbitrary code or crash the device, compromising network security for all connected devices.

Affected Products

• D-Link DWR-M960 Firmware version 1.01.07
• D-Link DWR-M960 Hardware revision B1
• D-Link DWR-M960 4G LTE Router

Discovery Timeline

• 2026-02-21 - CVE-2026-2881 published to NVD
• 2026-02-23 - Last updated in NVD database

Technical Details for CVE-2026-2881

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw exists within the Advanced Firewall Configuration handler at the /boafrm/formFirewallAdv endpoint. When processing the submit-url parameter, the sub_425FF8 function fails to properly validate the length of user-supplied input before copying it to a fixed-size stack buffer.

The attack is network-accessible and requires low-privileged authentication to the router's web management interface. Once authenticated, an attacker can craft a malicious request containing an oversized submit-url parameter that overwrites adjacent stack memory, including the return address. This can lead to arbitrary code execution with the privileges of the web server process, typically running as root on embedded devices like this router.

Root Cause

The root cause is a classic stack-based buffer overflow stemming from insufficient bounds checking in the sub_425FF8 function. The function uses an unsafe memory copy operation that does not verify whether the input data fits within the allocated stack buffer. This allows attackers to write beyond the buffer boundaries, corrupting the stack frame and potentially hijacking program execution flow.

Attack Vector

The attack vector is network-based, targeting the router's web management interface. An attacker with valid credentials (or access to a compromised authenticated session) can send a specially crafted HTTP POST request to /boafrm/formFirewallAdv with a malicious submit-url parameter. The oversized input triggers the buffer overflow in the sub_425FF8 function.

The vulnerability can be exploited by sending an HTTP POST request to the firewall configuration endpoint with an excessively long submit-url parameter value. The malicious input overflows the stack buffer in the sub_425FF8 function, potentially allowing the attacker to overwrite the return address and redirect execution to attacker-controlled code. Technical details and proof-of-concept information have been disclosed through the GitHub Issue Discussion.

Detection Methods for CVE-2026-2881

Indicators of Compromise

• Unexpected HTTP POST requests to /boafrm/formFirewallAdv with abnormally long submit-url parameter values
• Router crashes or unexpected reboots following web interface access
• Unusual outbound network connections from the router to unknown destinations
• Modified firewall rules or configuration changes not authorized by administrators

Detection Strategies

• Monitor web server access logs for requests to /boafrm/formFirewallAdv with parameter lengths exceeding normal thresholds
• Implement network intrusion detection rules to identify HTTP requests containing oversized POST data targeting D-Link router endpoints
• Deploy behavioral monitoring to detect abnormal router process crashes or memory access violations
• Review authentication logs for unusual login patterns preceding potential exploitation attempts

Monitoring Recommendations

• Enable detailed logging on the D-Link DWR-M960 web management interface if supported
• Configure network monitoring tools to alert on large HTTP POST requests to router management endpoints
• Implement automated reboot monitoring to detect potential exploitation-induced crashes
• Consider deploying a web application firewall (WAF) in front of router management interfaces on critical network segments

How to Mitigate CVE-2026-2881

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management access if not required for operations
• Implement strong authentication credentials and enable HTTPS for the management interface
• Place the router's management interface on a separate, isolated management VLAN
• Monitor for firmware updates from D-Link addressing this vulnerability

Patch Information

As of the last update on 2026-02-23, no official patch has been released by D-Link for this vulnerability. Administrators should regularly check the D-Link Security Resource page for firmware updates addressing CVE-2026-2881. Additional technical details are available through VulDB #347175.

Workarounds

• Configure firewall rules to block external access to the router's management interface (port 80/443)
• Use access control lists (ACLs) to limit management access to specific administrator IP addresses
• Consider placing a reverse proxy with input validation in front of the management interface
• Disable the web management interface entirely and use alternative management methods if available

# Example iptables rules to restrict management interface access
# Apply these on an upstream firewall protecting the router

# Block external access to router management (assuming router IP is 192.168.1.1)
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP

# Allow only specific admin workstation (192.168.1.100) to access management
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 443 -j ACCEPT