CVE-2026-5613 Overview
A stack-based buffer overflow vulnerability has been identified in the Belkin F9K1015 wireless router firmware version 1.00.10. This vulnerability exists in the formReboot function within the /goform/formReboot endpoint, where improper handling of the webpage argument allows attackers to trigger a buffer overflow condition. The vulnerability can be exploited remotely by authenticated attackers, potentially leading to arbitrary code execution or denial of service on the affected device.
Critical Impact
Remote attackers with low-privilege access can exploit this stack-based buffer overflow to potentially execute arbitrary code, compromise device integrity, or cause denial of service on vulnerable Belkin F9K1015 routers.
Affected Products
- Belkin F9K1015 Wireless Router firmware version 1.00.10
- Belkin F9K1015 devices with /goform/formReboot endpoint exposed
Discovery Timeline
- 2026-04-06 - CVE-2026-5613 published to NVD
- 2026-04-07 - Last updated in NVD database
Technical Details for CVE-2026-5613
Vulnerability Analysis
This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), specifically manifesting as a stack-based buffer overflow. The vulnerable function formReboot fails to properly validate the length of input provided through the webpage argument before copying it to a fixed-size stack buffer.
The exploitation mechanism relies on the network-accessible nature of the router's web management interface. An attacker with valid credentials (low privilege requirement) can send a specially crafted HTTP request to the /goform/formReboot endpoint with an oversized webpage parameter. This causes the function to write beyond the allocated stack buffer boundaries, potentially overwriting critical stack data including return addresses and saved registers.
The exploit has been publicly disclosed through vulnerability databases and security research repositories. The vendor was contacted regarding this disclosure but did not respond, leaving affected devices without an official patch. This lack of vendor engagement increases the risk profile for organizations using these devices.
Root Cause
The root cause of this vulnerability lies in the absence of proper bounds checking when processing user-supplied input in the formReboot function. The firmware code copies the webpage argument directly into a stack-allocated buffer without verifying that the input length does not exceed the buffer's capacity. This classic memory safety issue allows attackers to overflow the buffer and corrupt adjacent stack memory, which can be leveraged to hijack program execution flow.
Attack Vector
The attack is conducted over the network against the router's web management interface. An attacker must have low-level authentication credentials to access the /goform/formReboot endpoint. Once authenticated, the attacker crafts a malicious HTTP request containing an oversized value for the webpage parameter. When the vulnerable formReboot function processes this request, the buffer overflow occurs on the stack.
The exploitation flow involves:
- Authentication to the router's web interface with valid credentials
- Sending a crafted POST request to /goform/formReboot
- Including a maliciously long webpage parameter value
- Triggering the stack buffer overflow in the formReboot function
- Potentially achieving code execution or causing device crash
Technical details and proof-of-concept information are available through the GitHub Documentation for Belkin Vulnerability and VulDB #355404.
Detection Methods for CVE-2026-5613
Indicators of Compromise
- Unusual HTTP POST requests to /goform/formReboot with abnormally long parameter values
- Router crashes or unexpected reboots following web interface access
- Network traffic showing requests with oversized webpage parameter in HTTP body
- Evidence of unauthorized authentication attempts to the router management interface
Detection Strategies
- Monitor network traffic for HTTP requests to /goform/formReboot endpoints with payload sizes exceeding normal parameters
- Implement intrusion detection rules to flag requests containing excessively long webpage parameter values
- Review router access logs for suspicious authentication patterns followed by requests to the vulnerable endpoint
- Deploy network-based anomaly detection to identify potential buffer overflow attack patterns
Monitoring Recommendations
- Enable comprehensive logging on network security appliances monitoring traffic to IoT and embedded devices
- Configure alerts for any access attempts to /goform/formReboot from untrusted network segments
- Implement continuous monitoring of Belkin router behavior for signs of compromise or instability
- Establish baseline traffic patterns for router management interfaces to detect anomalies
How to Mitigate CVE-2026-5613
Immediate Actions Required
- Restrict network access to the router's web management interface using firewall rules or ACLs
- Disable remote management features if not required for operations
- Implement network segmentation to isolate vulnerable IoT devices from critical systems
- Consider replacing vulnerable Belkin F9K1015 devices with supported alternatives that receive security updates
- Enforce strong, unique credentials for router administrative access
Patch Information
No official patch is currently available from Belkin. According to the vulnerability disclosure, the vendor was contacted early about this issue but did not respond. Organizations should implement compensating controls until a patch becomes available or consider device replacement.
For additional technical details, refer to:
Workarounds
- Block external access to the router's web management interface at the network perimeter
- Configure firewall rules to allow management access only from trusted administrative workstations
- Implement a VPN requirement for any remote administration needs
- Regularly audit network device inventory and remove unsupported devices from production environments
# Example firewall rule to restrict management interface access (iptables)
# Allow management access only from trusted admin subnet
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
# Block external access to goform endpoints at network perimeter
iptables -A FORWARD -p tcp --dport 80 -m string --string "/goform/" --algo bm -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
