CVE-2026-3698: UTT 810G Firmware Buffer Overflow Flaw

CVE-2026-3698 Overview

A critical buffer overflow vulnerability has been identified in UTT HiPER 810G routers running firmware versions up to 1.7.7-171114. This vulnerability affects the strcpy function within the /goform/NTP endpoint, allowing remote attackers to exploit improper boundary checks and potentially execute arbitrary code or cause denial of service conditions on affected devices.

Critical Impact

Remote attackers with low privileges can exploit this buffer overflow vulnerability over the network to compromise UTT HiPER 810G routers, potentially leading to complete device takeover, arbitrary code execution, or service disruption.

Affected Products

• UTT HiPER 810G Firmware versions up to 1.7.7-171114
• UTT 810G Hardware revision 3.0
• UTT 810G Firmware (all versions prior to patch)

Discovery Timeline

• 2026-03-08 - CVE-2026-3698 published to NVD
• 2026-03-10 - Last updated in NVD database

Technical Details for CVE-2026-3698

Vulnerability Analysis

This buffer overflow vulnerability exists due to unsafe use of the strcpy function in the /goform/NTP handler of the UTT HiPER 810G router firmware. The strcpy function copies a source string to a destination buffer without verifying that the destination buffer has sufficient space to hold the input data. When an attacker supplies an overly long input string to this endpoint, the function writes beyond the allocated buffer boundaries, corrupting adjacent memory regions.

This type of memory corruption falls under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), which represents a fundamental class of vulnerabilities in systems programming. The vulnerability can be exploited remotely over the network by authenticated users with low privileges, requiring no user interaction. Successful exploitation could allow attackers to crash the device, execute arbitrary code with elevated privileges, or gain persistent access to the router.

Root Cause

The root cause of this vulnerability is the improper use of the strcpy function without proper bounds checking in the /goform/NTP endpoint handler. The firmware code accepts user-supplied input and passes it directly to strcpy, which performs an unbounded memory copy operation. Without validation of the input length against the destination buffer size, attackers can overflow the buffer by supplying input that exceeds the expected boundaries.

Attack Vector

The attack can be initiated remotely over the network against the router's web management interface. An attacker with low-level authentication to the device can craft a malicious HTTP request to the /goform/NTP endpoint containing an oversized payload. When the vulnerable strcpy function processes this input, the buffer overflow occurs, allowing the attacker to overwrite critical memory structures such as return addresses, function pointers, or other control data.

The vulnerability is exploitable with the following characteristics:

• Remote exploitation via the network-accessible web interface
• Low authentication required - authenticated access needed but with minimal privileges
• No user interaction required - exploitation can be automated
• Public exploit availability - exploit details are publicly documented

The GitHub CVE Vulnerability Document provides additional technical details about the exploitation methodology.

Detection Methods for CVE-2026-3698

Indicators of Compromise

• Unusual HTTP POST requests to /goform/NTP containing abnormally large payloads
• Router crashes or unexpected reboots following web interface access
• Anomalous network traffic patterns originating from the router
• Unexpected changes to router configuration or firmware

Detection Strategies

• Monitor web server logs for requests to /goform/NTP with payload sizes exceeding normal operational parameters
• Implement network intrusion detection rules to identify buffer overflow attack patterns targeting UTT devices
• Deploy SentinelOne Singularity to detect exploit attempts and post-exploitation behavior on network segments containing affected routers
• Review access logs for repeated authentication attempts followed by suspicious endpoint access

Monitoring Recommendations

• Enable verbose logging on UTT HiPER 810G devices if supported by firmware
• Configure network monitoring tools to alert on HTTP requests with oversized Content-Length headers to /goform/ endpoints
• Establish baseline network behavior for router management traffic and alert on deviations
• Implement periodic integrity checks on router configurations to detect unauthorized modifications

How to Mitigate CVE-2026-3698

Immediate Actions Required

• Restrict network access to the UTT HiPER 810G web management interface using firewall rules or ACLs
• Limit management interface access to trusted internal networks only; disable WAN-side administration
• Implement strong authentication credentials and review user accounts with router access
• Consider taking affected devices offline if they are exposed to untrusted networks until a patch is available

Patch Information

At the time of publication, no vendor patch has been confirmed for this vulnerability. Organizations should monitor UTT's official channels for firmware updates addressing this buffer overflow issue. The following resources provide additional context:

• VulDB #349644 Incident Report
• VulDB #349644 Detailed Analysis

Workarounds

• Implement network segmentation to isolate affected routers from untrusted network segments
• Deploy a web application firewall (WAF) or reverse proxy in front of the management interface to filter malicious requests
• Disable the NTP configuration feature through the web interface if not required for operations
• Consider replacing affected devices with alternative hardware if patch availability is delayed

# Example: Restrict management interface access via firewall rules
# Block external access to router management port (example for upstream firewall)
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 management access only from trusted admin subnet
iptables -I FORWARD -s 192.168.100.0/24 -d <ROUTER_IP> -p tcp --dport 80 -j ACCEPT
iptables -I FORWARD -s 192.168.100.0/24 -d <ROUTER_IP> -p tcp --dport 443 -j ACCEPT