CVE-2025-6732: UTT HiPER 840G Buffer Overflow Vulnerability

CVE-2025-6732 Overview

CVE-2025-6732 is a buffer overflow vulnerability in UTT HiPER 840G routers running firmware versions up to 3.1.1-190328. The flaw resides in the strcpy call within the /goform/setSysAdm endpoint of the device API. Attackers can trigger the overflow by manipulating the passwd1 argument, which is copied without bounds checking. The vulnerability is remotely exploitable and the exploit details have been publicly disclosed. The vendor was contacted about the disclosure but did not respond. The weakness is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer).

Critical Impact
Remote attackers with low privileges can corrupt memory on affected UTT HiPER 840G devices, potentially leading to arbitrary code execution or denial of service on network infrastructure.

Affected Products

UTT HiPER 840G router (hardware version 3.0)
UTT 840G firmware versions up to 3.1.1-190328
Deployments exposing the /goform/setSysAdm API endpoint

Discovery Timeline

2025-06-26 - CVE-2025-6732 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-6732

Vulnerability Analysis

The vulnerability exists in the administrative API handler for /goform/setSysAdm on UTT HiPER 840G devices. The handler processes password change requests submitted through the web-based management interface. When processing the passwd1 HTTP parameter, the firmware invokes strcpy to copy the attacker-controlled value into a fixed-size stack buffer. Because strcpy performs no length validation, an oversized passwd1 value overwrites adjacent memory, including saved return addresses and control structures. This memory corruption can be leveraged to hijack execution flow on the device.

The EPSS score for this vulnerability stands at 0.795%, placing it in the 51st percentile for exploitation likelihood. The publicly available proof-of-concept increases the probability of opportunistic scanning and exploitation against exposed devices.

Root Cause

The root cause is the use of unsafe C string handling in the setSysAdm API handler. The firmware copies untrusted request data directly with strcpy rather than a bounded routine such as strncpy or strlcpy. No input length validation is applied to the passwd1 parameter before the copy occurs, making stack corruption trivial once the parameter exceeds the destination buffer size.

Attack Vector

Exploitation requires network access to the device management interface and low-privileged authentication. An attacker submits a crafted HTTP POST request to /goform/setSysAdm with an oversized passwd1 value. The overflow occurs during request processing, corrupting the stack and enabling control over the instruction pointer. Devices with the management interface exposed to untrusted networks face the highest risk.

// Vulnerable pattern (illustrative, based on public advisory)
// POST /goform/setSysAdm HTTP/1.1
// Host: <router-ip>
// Content-Type: application/x-www-form-urlencoded
//
// passwd1=<oversized string exceeding destination buffer>
//
// Handler performs: strcpy(local_buffer, passwd1_value);
// No length check -> stack buffer overflow

Technical details are documented in the GitHub CVE Document and VulDB entry #314007.

Detection Methods for CVE-2025-6732

Indicators of Compromise

HTTP POST requests to /goform/setSysAdm containing abnormally long passwd1 parameter values
Unexpected reboots, crashes, or watchdog resets on UTT HiPER 840G devices
New administrative sessions or configuration changes on the router following anomalous API traffic
Outbound connections from the router to unfamiliar hosts, indicating potential post-exploitation activity

Detection Strategies

Deploy network intrusion detection signatures matching POST requests to /goform/setSysAdm with passwd1 parameter lengths exceeding typical password bounds (for example, greater than 64 bytes)
Monitor router syslog and management logs for repeated authentication failures or malformed requests preceding crashes
Correlate device availability alerts with web management traffic to identify overflow-induced denial of service

Monitoring Recommendations

Log and inspect all HTTP traffic destined for the router administrative interface, including request body sizes
Baseline normal management traffic patterns and alert on deviations targeting goform endpoints
Track firmware versions across the router fleet to identify devices still running vulnerable builds up to 3.1.1-190328

How to Mitigate CVE-2025-6732

Immediate Actions Required

Restrict access to the router web management interface to trusted administrative networks only, blocking WAN-side exposure
Enforce strong administrator credentials and disable any default or shared accounts on affected devices
Segment UTT HiPER 840G devices from user networks and monitor management-plane traffic for anomalies
Inventory all UTT HiPER 840G units and identify those running firmware versions up to 3.1.1-190328

Patch Information

At the time of publication, no vendor patch has been released. The vendor was contacted early about this disclosure but did not respond. Organizations should treat all firmware versions up to 3.1.1-190328 as vulnerable and monitor UTT communications for future security updates.

Workarounds

Disable remote management on the WAN interface and bind the administrative service to internal management VLANs only
Place the device behind a firewall that filters access to /goform/setSysAdm from untrusted sources
Consider replacing affected devices with actively maintained network equipment if the vendor remains unresponsive

bash

# Example firewall rule to restrict access to the router management interface
# Replace <mgmt-subnet> and <router-ip> with your environment values
iptables -A FORWARD -p tcp -s <mgmt-subnet> -d <router-ip> --dport 80 -j ACCEPT
iptables -A FORWARD -p tcp -d <router-ip> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <router-ip> --dport 443 -j DROP