CVE-2026-2935: UTT 810G Firmware Buffer Overflow Flaw

CVE-2026-2935 Overview

A buffer overflow vulnerability has been identified in UTT HiPER 810G routers running firmware versions up to 1.7.7-171114. This issue affects the strcpy function within the /goform/ConfigExceptMSN endpoint, where improper handling of the remark argument allows an attacker to trigger a buffer overflow condition. The vulnerability can be exploited remotely over the network by authenticated users with high privileges.

Critical Impact

Successful exploitation of this buffer overflow vulnerability could allow remote attackers to execute arbitrary code, crash the device, or gain complete control over the affected UTT HiPER 810G router, potentially compromising the entire network infrastructure.

Affected Products

• UTT HiPER 810G Firmware up to version 1.7.7-171114
• UTT HiPER 810G Hardware version 3.0

Discovery Timeline

• 2026-02-22 - CVE-2026-2935 published to NVD
• 2026-02-24 - Last updated in NVD database

Technical Details for CVE-2026-2935

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw exists in the web management interface of the UTT HiPER 810G router, specifically within the form handler at /goform/ConfigExceptMSN. The vulnerable code uses the strcpy function to copy user-supplied input from the remark parameter without proper bounds checking, leading to a classic stack-based buffer overflow condition.

When an attacker submits an overly long string to the remark parameter, the strcpy function writes beyond the allocated buffer boundaries, potentially overwriting adjacent memory including return addresses and other critical stack data. This can lead to denial of service through device crashes, or in more sophisticated attacks, arbitrary code execution on the affected device.

Root Cause

The root cause of this vulnerability is the use of the unsafe strcpy function without proper input length validation. The strcpy function does not perform bounds checking and will continue copying data until it encounters a null terminator, regardless of the destination buffer size. This unsafe coding practice in embedded firmware is particularly dangerous as it can lead to complete device compromise.

Attack Vector

The attack is network-based and can be executed remotely against the device's web management interface. An attacker with high-level privileges (authenticated administrator access) can craft a malicious HTTP POST request to the /goform/ConfigExceptMSN endpoint with an oversized remark parameter value. The exploit has been publicly disclosed, increasing the risk of active exploitation attempts. The attack requires no user interaction beyond having network access to the device's management interface.

The vulnerability mechanism involves sending a specially crafted HTTP POST request to the vulnerable endpoint. When the remark parameter contains a string longer than the allocated buffer size, the strcpy function overwrites adjacent memory locations, potentially allowing control of program execution flow. For detailed technical analysis, refer to the GitHub Issue Discussion and VulDB entry #347297.

Detection Methods for CVE-2026-2935

Indicators of Compromise

• Unexpected device reboots or crashes, particularly when accessing the web management interface
• Anomalous HTTP POST requests to /goform/ConfigExceptMSN with unusually long remark parameter values
• Unusual network traffic patterns originating from the router's management interface
• Evidence of unauthorized configuration changes or new user accounts on the device

Detection Strategies

• Implement network-based intrusion detection rules to identify HTTP POST requests to /goform/ConfigExceptMSN containing abnormally long parameter values
• Monitor web server logs on the device for repeated requests to the vulnerable endpoint
• Deploy SentinelOne network monitoring to detect exploitation attempts and buffer overflow attack patterns
• Configure alerts for any unusual authentication activity to the router's management interface

Monitoring Recommendations

• Enable verbose logging on the UTT HiPER 810G device if available
• Implement network traffic analysis for all traffic to and from the device's management interface
• Set up automated alerts for device availability to detect crash conditions
• Review access logs regularly for suspicious authentication attempts or unusual POST request patterns

How to Mitigate CVE-2026-2935

Immediate Actions Required

• Restrict network access to the device's web management interface to trusted IP addresses only
• Implement firewall rules to block external access to the management interface (typically port 80/443)
• Review and audit all administrative accounts on the device, removing unnecessary privileged access
• Consider placing the management interface on a dedicated, isolated VLAN

Patch Information

At the time of publication, no vendor patch has been officially announced for this vulnerability. Organizations should monitor UTT's official channels and the GitHub Issue Discussion for updates regarding firmware patches. Given the public disclosure of this vulnerability, applying patches immediately upon availability is strongly recommended.

Workarounds

• Disable remote web management access and use local console access only when configuration changes are required
• Implement network segmentation to isolate the affected device from untrusted networks
• Deploy a Web Application Firewall (WAF) or reverse proxy in front of the management interface to filter malicious requests
• Consider replacing the vulnerable device with an alternative solution if patching timeline is uncertain

# Example firewall configuration to restrict management access
# Allow management access only from trusted admin workstation
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP