CVE-2026-3700: UTT 810G Firmware Buffer Overflow Flaw

CVE-2026-3700 Overview

A buffer overflow vulnerability has been identified in UTT HiPER 810G routers running firmware versions up to 1.7.7-171114. The vulnerability exists in the strcpy function within the /goform/formConfigDnsFilterGlobal endpoint. This flaw allows attackers to cause a buffer overflow condition through manipulation of input parameters. Remote exploitation is possible over the network, and proof-of-concept exploit code has been made publicly available, increasing the risk of active exploitation attempts.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability to potentially execute arbitrary code, crash the device, or gain unauthorized control over affected UTT HiPER 810G routers. The public availability of exploit code significantly increases the likelihood of attacks against unpatched devices.

Affected Products

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

Discovery Timeline

• 2026-03-08 - CVE-2026-3700 published to NVD
• 2026-03-10 - Last updated in NVD database

Technical Details for CVE-2026-3700

Vulnerability Analysis

This vulnerability affects the DNS Filter Global configuration handler in UTT HiPER 810G routers. The vulnerable code path involves the strcpy function processing user-supplied input without proper bounds checking. When exploited, the buffer overflow can overwrite adjacent memory regions, potentially allowing an attacker to hijack program execution flow or cause denial of service conditions. The attack can be carried out remotely over the network by authenticated users with low-level privileges, requiring no user interaction.

Root Cause

The root cause is improper restriction of operations within the bounds of a memory buffer (CWE-119). The vulnerable firmware uses the unsafe strcpy function to copy user-controlled input into a fixed-size buffer within the /goform/formConfigDnsFilterGlobal form handler. Since strcpy does not perform length validation, supplying input exceeding the destination buffer size results in adjacent memory being overwritten.

Attack Vector

The attack vector is network-based, targeting the web management interface of the UTT HiPER 810G router. An attacker with low-level authentication can send specially crafted HTTP requests to the /goform/formConfigDnsFilterGlobal endpoint. By manipulating parameters processed by the vulnerable strcpy function, the attacker can trigger a buffer overflow condition.

The vulnerability manifests in the DNS Filter Global configuration form handler where user input is copied without proper boundary validation. For technical details and proof-of-concept information, refer to the GitHub PoC Repository and the VulDB entry.

Detection Methods for CVE-2026-3700

Indicators of Compromise

• Unexpected HTTP POST requests to /goform/formConfigDnsFilterGlobal containing unusually long parameter values
• Router crashes or unexpected reboots following web interface access
• Anomalous network traffic patterns originating from the router management interface
• Authentication logs showing access to configuration endpoints from unexpected sources

Detection Strategies

• Monitor web server logs for requests to /goform/formConfigDnsFilterGlobal with oversized payloads
• Implement intrusion detection rules to identify buffer overflow attack patterns targeting UTT router endpoints
• Deploy network monitoring to detect exploitation attempts against router management interfaces
• Enable logging on the router management interface to capture suspicious configuration requests

Monitoring Recommendations

• Establish baseline traffic patterns for router management interface access and alert on deviations
• Configure SIEM rules to correlate authentication events with configuration endpoint access
• Monitor for unexpected outbound connections from router devices that could indicate compromise
• Regularly review router logs for signs of exploitation attempts or unauthorized access

How to Mitigate CVE-2026-3700

Immediate Actions Required

• Restrict access to the router management interface to trusted IP addresses only
• Implement network segmentation to isolate router management interfaces from untrusted networks
• Disable remote management access if not required for operations
• Monitor for and block exploitation attempts at the network perimeter
• Consider deploying a web application firewall to filter malicious requests targeting the vulnerable endpoint

Patch Information

At the time of publication, no official vendor patch has been identified. Organizations should check UTT's official channels for firmware updates addressing CVE-2026-3700. Additional technical details are available through VulDB CTI ID #349646 and the VulDB submission.

Workarounds

• Implement strict access control lists (ACLs) limiting management interface access to authorized administrator IP addresses
• Place affected routers behind a firewall that blocks external access to the web management interface
• Use VPN connectivity for remote administration rather than exposing the management interface directly
• Consider replacing affected devices with alternative hardware if vendor patches are not forthcoming

# Example: Restrict management interface access via firewall rules
# Block external access to router management port (typically 80/443)
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP