CVE-2026-2855 Overview
CVE-2026-2855 is a stack-based buffer overflow in the D-Link DWR-M960 router running firmware version 1.01.07. The flaw resides in the sub_4648F0 function within /boafrm/formDdns, which handles DDNS Settings requests. Attackers can trigger the overflow by manipulating the submit-url argument, corrupting stack memory on the device. The attack is initiated remotely and requires low-privilege authentication. Public disclosure of the exploit increases the risk of opportunistic abuse against exposed devices. The vulnerability is categorized under [CWE-119] for improper restriction of operations within memory bounds.
Critical Impact
Remote authenticated attackers can corrupt stack memory through a malformed submit-url parameter, enabling potential code execution or device compromise on the DWR-M960 router.
Affected Products
- D-Link DWR-M960 firmware version 1.01.07
- D-Link DWR-M960 hardware revision B1
- Deployments exposing the web management interface (/boafrm/formDdns)
Discovery Timeline
- 2026-02-20 - CVE-2026-2855 published to NVD
- 2026-02-23 - Last updated in NVD database
Technical Details for CVE-2026-2855
Vulnerability Analysis
The vulnerability exists in the DDNS Settings Handler component of the DWR-M960 web management interface. The sub_4648F0 function processes HTTP requests submitted to /boafrm/formDdns without adequately validating the length of user-supplied input. When an attacker sends a request containing an oversized submit-url argument, the function copies the value into a fixed-size stack buffer, overrunning adjacent memory regions.
Stack-based buffer overflows on embedded MIPS or ARM router firmware typically allow attackers to overwrite the saved return address and redirect execution. Successful exploitation can lead to arbitrary code execution within the context of the web server process, which generally runs with elevated privileges on consumer-grade D-Link routers.
Because the attack vector is network-based and requires only low privileges, an authenticated user on the local network or an attacker with valid credentials reachable over the internet can deliver the payload.
Root Cause
The root cause is the absence of bounds checking on the submit-url parameter before it is copied into a stack-allocated buffer inside sub_4648F0. The function trusts attacker-controlled input length, violating safe memory handling practices outlined in [CWE-119].
Attack Vector
An attacker authenticates to the router web interface and submits a crafted POST request to /boafrm/formDdns containing an overlong submit-url value. The malformed parameter overflows the destination buffer, corrupting the call stack. The exploit has been publicly disclosed, lowering the bar for reproduction.
No verified exploitation code is available from authoritative sources. Refer to the GitHub Issue Discussion and the VulDB #347094 entry for technical analysis.
Detection Methods for CVE-2026-2855
Indicators of Compromise
- HTTP POST requests to /boafrm/formDdns containing abnormally long submit-url parameter values
- Unexpected reboots, crashes, or watchdog resets of the DWR-M960 web administration service
- Outbound connections from the router to unknown hosts following DDNS configuration changes
- New or modified administrative accounts on the device after suspicious web traffic
Detection Strategies
- Inspect web access logs on upstream proxies or IDS sensors for requests targeting /boafrm/formDdns with payload lengths exceeding typical DDNS URL sizes
- Deploy network signatures matching oversized submit-url parameters in form submissions to D-Link router endpoints
- Correlate router management interface authentication events with subsequent crash or reboot indicators
Monitoring Recommendations
- Restrict and log access to router administrative interfaces using network segmentation and ACLs
- Forward router syslog data to a centralized logging platform for anomaly review
- Alert on any external IP addresses attempting to reach the DWR-M960 management interface
How to Mitigate CVE-2026-2855
Immediate Actions Required
- Disable remote (WAN-side) access to the router web management interface
- Restrict LAN-side management access to a dedicated administrative VLAN or trusted IP allowlist
- Rotate administrative credentials and disable unused accounts on affected DWR-M960 devices
- Monitor the D-Link Security Overview page for firmware updates addressing CVE-2026-2855
Patch Information
No vendor patch has been published at the time of NVD disclosure. Administrators should consult the D-Link Security Overview for future advisories and updated firmware for the DWR-M960 hardware revision B1 running firmware 1.01.07.
Workarounds
- Place the router behind an upstream firewall that blocks inbound HTTP/HTTPS connections to the management interface
- Disable the DDNS feature if it is not required for operational use
- Replace end-of-support D-Link DWR-M960 units with currently supported hardware where feasible
# Example: block external access to the router management interface upstream
iptables -I FORWARD -p tcp -d <router-lan-ip> --dport 80 -m iprange ! --src-range <admin-allowlist> -j DROP
iptables -I FORWARD -p tcp -d <router-lan-ip> --dport 443 -m iprange ! --src-range <admin-allowlist> -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
