CVE-2026-3699: UTT 810G Firmware Buffer Overflow Flaw

CVE-2026-3699 Overview

A critical buffer overflow vulnerability has been discovered in UTT HiPER 810G router firmware up to version 1.7.7-171114. The vulnerability exists in the strcpy function within the /goform/formRemoteControl file, allowing remote attackers to exploit improper buffer bounds checking. This security flaw enables attackers to potentially execute arbitrary code or cause denial of service conditions on affected network devices.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability over the network to compromise UTT HiPER 810G routers, potentially gaining unauthorized access to network infrastructure or disrupting network services.

Affected Products

• UTT HiPER 810G firmware versions up to 1.7.7-171114
• UTT 810G hardware version 3.0
• UTT 810G firmware (all versions prior to patched release)

Discovery Timeline

• 2026-03-08 - CVE-2026-3699 published to NVD
• 2026-03-10 - Last updated in NVD database

Technical Details for CVE-2026-3699

Vulnerability Analysis

This buffer overflow vulnerability (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer) occurs due to unsafe use of the strcpy function in the remote control form handler. The strcpy function does not perform bounds checking when copying data, which allows attackers to write beyond the allocated buffer boundaries when submitting malicious input to the /goform/formRemoteControl endpoint.

The vulnerability is exploitable remotely over the network and requires low attack complexity with minimal privileges. Successful exploitation could result in complete compromise of the device's confidentiality, integrity, and availability, potentially allowing attackers to execute arbitrary code with elevated privileges on the router.

Root Cause

The root cause of this vulnerability is the improper use of the unsafe strcpy function for handling user-supplied input in the form processing code. The strcpy function copies data without verifying that the destination buffer is large enough to accommodate the source data, leading to a classic buffer overflow condition. When user-controlled input exceeds the expected buffer size, adjacent memory regions are overwritten, which can corrupt program execution flow.

Attack Vector

The attack vector is network-based, targeting the web management interface of UTT HiPER 810G routers. An attacker can craft a malicious HTTP request to the /goform/formRemoteControl endpoint containing an oversized payload. When this payload is processed by the vulnerable strcpy function, it triggers the buffer overflow condition.

The vulnerability requires network access to the router's management interface and low-level authentication. The exploit has been disclosed publicly, increasing the risk of widespread exploitation against unpatched devices.

The vulnerability manifests in the form processing function that handles remote control requests. When user input is passed to strcpy without proper length validation, the buffer boundary can be exceeded. For detailed technical information, refer to the GitHub CVE Documentation.

Detection Methods for CVE-2026-3699

Indicators of Compromise

• Unusual HTTP POST requests to /goform/formRemoteControl with abnormally large parameter values
• Router exhibiting unexpected reboots or crashes after web interface access
• Anomalous network traffic patterns originating from the router's management interface
• Log entries showing repeated access attempts to the vulnerable form endpoint

Detection Strategies

• Deploy network intrusion detection rules to identify oversized HTTP requests targeting /goform/formRemoteControl
• Monitor web server logs for suspicious POST requests with payloads exceeding normal parameter lengths
• Implement application-layer firewall rules to validate and restrict input sizes to form endpoints
• Use SentinelOne Singularity to detect anomalous process behavior on network devices where agents can be deployed

Monitoring Recommendations

• Enable verbose logging on router management interfaces to capture request details
• Monitor for unusual memory consumption or crash patterns on UTT HiPER 810G devices
• Implement network segmentation to isolate router management interfaces from untrusted networks
• Regularly audit device configurations and access logs for signs of compromise

How to Mitigate CVE-2026-3699

Immediate Actions Required

• Restrict network access to the router's web management interface to trusted IP addresses only
• Disable remote management features if not required for operations
• Implement firewall rules to block external access to the /goform/formRemoteControl endpoint
• Monitor for vendor security advisories and apply firmware updates when available

Patch Information

At the time of publication, no official patch information has been released by UTT. Organizations should monitor the vendor's official channels for security updates. The vulnerability affects firmware versions up to 1.7.7-171114, and users should update to the latest available firmware once a patched version is released. For additional technical details, refer to VulDB #349645.

Workarounds

• Disable the web-based management interface and use console access only for device administration
• Implement a reverse proxy with input validation in front of the management interface
• Use network access control lists (ACLs) to restrict management interface access to specific administrator workstations
• Consider placing affected devices behind a VPN to limit exposure to trusted users only

# Example: Restrict management interface access via iptables (on upstream firewall)
# Block external access to router management port
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 443 -j DROP

# Allow access only from trusted management subnet
iptables -I FORWARD -s 10.0.0.0/24 -d <ROUTER_IP> -p tcp --dport 80 -j ACCEPT
iptables -I FORWARD -s 10.0.0.0/24 -d <ROUTER_IP> -p tcp --dport 443 -j ACCEPT