CVE-2026-3815: Utt 810g Firmware Buffer Overflow Flaw

CVE-2026-3815 Overview

A buffer overflow vulnerability has been identified in UTT HiPER 810G routers running firmware versions up to 1.7.7-1711. This vulnerability affects the strcpy function within the /goform/formApMail handler, allowing attackers to exploit improper boundary operations (CWE-119). The flaw enables remote attackers to trigger a buffer overflow condition that could result in system compromise. According to the vulnerability disclosure, an exploit for this vulnerability has been made publicly available, increasing the urgency for organizations to apply mitigations.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability to potentially execute arbitrary code or cause denial of service on affected UTT HiPER 810G routers through network-accessible endpoints.

Affected Products

• UTT HiPER 810G Hardware (version 3.0)
• UTT 810G Firmware (versions up to 1.7.7-1711)

Discovery Timeline

• 2026-03-09 - CVE-2026-3815 published to NVD
• 2026-03-10 - Last updated in NVD database

Technical Details for CVE-2026-3815

Vulnerability Analysis

This buffer overflow vulnerability stems from improper boundary operations within the UTT HiPER 810G firmware's web management interface. The vulnerable endpoint /goform/formApMail processes user-supplied input using the strcpy function without adequate bounds checking. When an attacker submits specially crafted input exceeding the expected buffer size, the function writes beyond the allocated memory boundaries, corrupting adjacent memory regions.

The vulnerability is remotely exploitable over the network without requiring user interaction. An attacker with low-level privileges (authenticated access to the web interface) can craft malicious requests to trigger the overflow condition. Successful exploitation could lead to complete compromise of the router's confidentiality, integrity, and availability.

Root Cause

The root cause is the use of the unsafe strcpy function without proper input length validation in the /goform/formApMail form handler. The strcpy function does not perform bounds checking, copying data until a null terminator is encountered. When processing untrusted input from HTTP POST parameters, the function copies user-supplied data into a fixed-size stack or heap buffer. Without validation that the input length does not exceed the destination buffer capacity, attackers can overflow the buffer with malicious data.

Attack Vector

The attack is conducted remotely via the network by sending specially crafted HTTP requests to the /goform/formApMail endpoint on the UTT HiPER 810G's web management interface. An authenticated attacker can manipulate form parameters to include oversized data payloads that trigger the buffer overflow when processed by the vulnerable strcpy function.

The attack sequence involves:

1. Accessing the device's web management interface
2. Authenticating with valid credentials (low privilege requirement)
3. Submitting a malicious POST request to /goform/formApMail with an oversized payload
4. The strcpy function copies the oversized input into a fixed-size buffer, overflowing into adjacent memory

For detailed technical analysis, refer to the GitHub Vulnerability Report.

Detection Methods for CVE-2026-3815

Indicators of Compromise

• Unusual HTTP POST requests to /goform/formApMail containing abnormally large parameter values
• Web server crashes or unexpected reboots of UTT HiPER 810G devices
• Suspicious network traffic patterns indicating automated exploitation attempts against the web management interface
• Anomalous memory consumption or process behavior on affected devices

Detection Strategies

• Implement network-level monitoring for HTTP traffic targeting /goform/formApMail endpoints with payload size anomalies
• Deploy intrusion detection signatures to identify buffer overflow exploitation patterns in POST request bodies
• Monitor device logs for repeated authentication attempts followed by web interface crashes
• Use SentinelOne Singularity to detect and block exploitation attempts targeting network infrastructure devices

Monitoring Recommendations

• Enable verbose logging on UTT HiPER 810G devices to capture all web interface access attempts
• Configure network monitoring tools to alert on large HTTP POST payloads to router management interfaces
• Implement continuous network traffic analysis to detect reconnaissance and exploitation attempts
• Review device stability metrics for unexpected restarts or service interruptions

How to Mitigate CVE-2026-3815

Immediate Actions Required

• Restrict access to the web management interface by implementing firewall rules to limit access to trusted IP addresses only
• Disable remote management access if not required for operational purposes
• Segment network infrastructure devices from general user networks to reduce attack surface
• Monitor for exploitation attempts using network intrusion detection systems

Patch Information

At the time of publication, no official vendor patch information is available in the CVE data. Organizations should monitor UTT's official channels for firmware updates that address CVE-2026-3815. Check the VulDB entry for updated remediation guidance.

Workarounds

• Restrict web management interface access to localhost or a dedicated management VLAN
• Implement strong authentication and change default credentials on affected devices
• Deploy a web application firewall (WAF) to filter malicious requests targeting the vulnerable endpoint
• Consider replacing affected devices with alternative network equipment if patches are not available

# Example firewall rule to restrict management interface access
# Allow only trusted management subnet to access web interface
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP