CVE-2026-5614: Belkin F9K1015 Buffer Overflow Vulnerability

CVE-2026-5614 Overview

CVE-2026-5614 is a stack-based buffer overflow vulnerability in the Belkin F9K1015 wireless router running firmware version 1.00.10. The flaw resides in the formSetPassword function exposed through the /goform/formSetPassword endpoint. Attackers can manipulate the webpage argument to trigger memory corruption on the stack. The attack is remotely exploitable over the network, and a public exploit has been released. Belkin was contacted by the reporter prior to disclosure but did not respond. The weakness is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer).

Critical Impact

Remote attackers with low privileges can corrupt router memory through the webpage parameter, potentially achieving arbitrary code execution on the device and full compromise of the network gateway.

Affected Products

• Belkin F9K1015 router (hardware revision)
• Belkin F9K1015 firmware version 1.00.10
• Deployments exposing the /goform/formSetPassword web management endpoint

Discovery Timeline

• 2026-04-06 - CVE-2026-5614 published to NVD
• 2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-5614

Vulnerability Analysis

The vulnerability exists in the HTTP handler formSetPassword, which processes password-change requests submitted to /goform/formSetPassword. The handler reads the webpage request parameter into a fixed-size stack buffer without enforcing length validation. Supplying an oversized value overruns the buffer and overwrites adjacent stack memory, including saved return addresses on MIPS or ARM-based embedded firmware. Successful exploitation leads to control of program flow and arbitrary code execution within the router's web server process, which typically runs with elevated privileges. Because the F9K1015 web interface is reachable from the LAN by default, and may be exposed to the WAN in misconfigured deployments, the attack surface extends to any authenticated user on the local network.

Root Cause

The root cause is improper bounds checking when copying the user-supplied webpage argument into a stack-allocated buffer inside formSetPassword. The function relies on unsafe string operations without validating input length, a recurring pattern in legacy goform-based router firmware.

Attack Vector

Exploitation requires the attacker to send a crafted HTTP POST request to /goform/formSetPassword containing an oversized webpage parameter. The attack is network-based, requires low privileges, and needs no user interaction. Public proof-of-concept material is referenced in the GitHub Vulnerability Report and VulDB entry #355405.

No verified exploit code is reproduced here. Refer to the public advisories for technical specifics of the payload structure.

Detection Methods for CVE-2026-5614

Indicators of Compromise

• HTTP POST requests to /goform/formSetPassword containing unusually long webpage parameter values exceeding typical form field sizes.
• Crashes, reboots, or service restarts of the router's embedded web server (httpd) following inbound management traffic.
• Unexpected configuration changes to administrator credentials or DNS settings on Belkin F9K1015 devices.

Detection Strategies

• Inspect network traffic for HTTP requests targeting /goform/formSetPassword with payload sizes that exceed expected length thresholds for the webpage field.
• Deploy intrusion detection signatures matching long parameter values in goform POST bodies on TCP/80 destined for Belkin device IP ranges.
• Correlate router reboot events with preceding inbound management HTTP traffic to identify exploitation attempts.

Monitoring Recommendations

• Forward router syslog and authentication events to a centralized logging platform for retention and correlation.
• Monitor DHCP, DNS, and gateway configuration drift for unauthorized changes consistent with post-exploitation activity.
• Track HTTP request anomalies to embedded device management interfaces using network detection tooling.

How to Mitigate CVE-2026-5614

Immediate Actions Required

• Restrict access to the router's web management interface to trusted management VLANs or hosts only.
• Ensure WAN-side remote management is disabled on all F9K1015 devices.
• Change default and shared administrator passwords to limit pre-authentication exposure where applicable.
• Plan migration to a supported router platform, given the vendor's lack of response to disclosure.

Patch Information

No vendor patch is available. According to the disclosure, Belkin was contacted but did not respond. Until an official fix is released, mitigations rely on network segmentation and device replacement.

Workarounds

• Place affected routers behind a separate firewall and block external access to TCP/80 and TCP/443 management ports.
• Use a network ACL or upstream router rule to drop HTTP requests targeting /goform/formSetPassword from untrusted segments.
• Disable the web administration interface when not actively in use and rely on local console access for configuration.

# Example iptables rule on an upstream Linux gateway
# Blocks WAN-side access to the F9K1015 web interface (replace <router_ip>)
iptables -I FORWARD -p tcp -d <router_ip> --dport 80 -i <wan_iface> -j DROP
iptables -I FORWARD -p tcp -d <router_ip> --dport 443 -i <wan_iface> -j DROP