CVE-2026-5614: Belkin F9K1015 Buffer Overflow Vulnerability

CVE-2026-5614 Overview

A stack-based buffer overflow vulnerability has been discovered in the Belkin F9K1015 wireless router firmware version 1.00.10. The vulnerability exists in the formSetPassword function located at /goform/formSetPassword, where improper handling of the webpage argument allows an attacker to trigger a buffer overflow condition. This firmware vulnerability can be exploited remotely over the network, potentially allowing attackers to execute arbitrary code or cause denial of service on affected devices.

Critical Impact

Remote attackers can exploit this stack-based buffer overflow to potentially gain full control of the affected router, compromising network security and enabling further lateral movement within the network.

Affected Products

• Belkin F9K1015 Wireless Router - Firmware version 1.00.10

Discovery Timeline

• 2026-04-06 - CVE-2026-5614 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2026-5614

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the web management interface of the Belkin F9K1015 router, specifically within the password configuration functionality. When processing HTTP requests to the /goform/formSetPassword endpoint, the formSetPassword function fails to properly validate the length of data supplied via the webpage parameter before copying it to a stack-allocated buffer.

The exploit has been publicly disclosed and may be actively used in attacks. The vendor was contacted regarding this vulnerability but did not respond, leaving affected devices without an official patch.

Root Cause

The root cause of this vulnerability is insufficient input validation and boundary checking in the formSetPassword function. When the webpage argument is processed, the function copies user-supplied data into a fixed-size buffer on the stack without verifying that the input length does not exceed the buffer's capacity. This classic buffer overflow condition allows attackers to overwrite adjacent memory on the stack, potentially including the return address, enabling control flow hijacking.

Attack Vector

The attack is network-accessible, meaning remote attackers can exploit this vulnerability without physical access to the device. The exploitation requires low privileges (authenticated access to the router's web interface) but requires no user interaction beyond the attacker's initial request. An attacker would craft a malicious HTTP POST request to the /goform/formSetPassword endpoint with an oversized webpage parameter value designed to overflow the stack buffer and overwrite critical memory structures.

The vulnerability mechanism involves sending a crafted request to the vulnerable endpoint. When the oversized input is processed by the formSetPassword function, the stack buffer overflows, potentially allowing the attacker to redirect code execution. Technical details and proof-of-concept information are available in the GitHub Vulnerability Report.

Detection Methods for CVE-2026-5614

Indicators of Compromise

• Anomalous HTTP POST requests to /goform/formSetPassword with unusually large parameter values
• Unexpected router reboots or crashes indicating potential exploitation attempts
• Unusual network traffic patterns originating from the router's management interface
• Log entries showing malformed requests to the password configuration endpoint

Detection Strategies

• Deploy network intrusion detection systems (IDS) with signatures to detect oversized requests to the vulnerable endpoint
• Monitor HTTP traffic to router management interfaces for requests containing abnormally long parameter values
• Implement web application firewall (WAF) rules to block requests exceeding expected parameter lengths for router administration endpoints
• Use SentinelOne Singularity to monitor network endpoints for suspicious lateral movement originating from router IP addresses

Monitoring Recommendations

• Enable verbose logging on network devices to capture all management interface access attempts
• Configure alerts for failed authentication attempts followed by requests to /goform/formSetPassword
• Monitor for unexpected firmware changes or configuration modifications on Belkin routers
• Implement network segmentation monitoring to detect traffic from compromised router devices

How to Mitigate CVE-2026-5614

Immediate Actions Required

• Restrict access to the router's web management interface to trusted internal networks only
• Disable remote administration features if enabled on the Belkin F9K1015
• Place affected routers behind a firewall that blocks external access to management ports
• Consider replacing affected Belkin F9K1015 devices with actively supported router models

Patch Information

No official patch is currently available from Belkin. The vendor was contacted early about this disclosure but did not respond. Users should consider the device end-of-life and plan for replacement with a supported router model. For additional technical details, refer to the VulDB Vulnerability Entry.

Workarounds

• Implement network access control lists (ACLs) to restrict management interface access to specific trusted IP addresses only
• Disable the web-based management interface entirely if command-line alternatives are available
• Deploy a network firewall between the router and untrusted networks to filter malicious requests
• Consider network segmentation to isolate the vulnerable device from critical network resources

# Configuration example - Firewall rule to restrict access to router management
# Block external access to router web interface (example using iptables on upstream device)
iptables -A FORWARD -p tcp --dport 80 -d <router_ip> -j DROP
iptables -A FORWARD -p tcp --dport 443 -d <router_ip> -j DROP
# Allow management access only from trusted admin subnet
iptables -I FORWARD -p tcp --dport 80 -s 192.168.1.0/24 -d <router_ip> -j ACCEPT