CVE-2025-7571: UTT 840G Firmware Buffer Overflow Flaw

CVE-2025-7571 Overview

CVE-2025-7571 is a buffer overflow vulnerability in UTT HiPER 840G routers running firmware versions up to 3.1.1-190328. The flaw resides in the /goform/aspApBasicConfigUrcp endpoint, where the Username parameter is not properly bounds-checked. An authenticated remote attacker can manipulate the parameter to trigger memory corruption in the device's web management interface. The exploit details have been publicly disclosed, increasing the risk of opportunistic attacks against exposed devices. UTT was contacted regarding the issue but did not respond to the disclosure.

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 against the router's management plane.

Affected Products

UTT HiPER 840G hardware (version 3.0)
UTT HiPER 840G firmware up to 3.1.1-190328
Deployments exposing the /goform/aspApBasicConfigUrcp web management endpoint

Discovery Timeline

2025-07-14 - CVE-2025-7571 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-7571

Vulnerability Analysis

The vulnerability is a classic buffer overflow [CWE-119] in the HTTP request handler for /goform/aspApBasicConfigUrcp. The handler copies the user-supplied Username argument into a fixed-size stack or heap buffer without enforcing length validation. When the input exceeds the destination buffer size, adjacent memory is overwritten. On embedded MIPS or ARM router targets like the HiPER 840G, this class of flaw typically allows control-flow hijacking through saved return address or function pointer corruption. The disclosed public proof-of-concept lowers the barrier to weaponization, and the vendor has not issued a fix.

Root Cause

The root cause is missing input length validation on the Username form field before it is processed by the aspApBasicConfigUrcp configuration handler. The web server, which runs with elevated privileges on the router, trusts the request payload and writes attacker-controlled bytes past the buffer boundary. This pattern is common in goform-based CGI handlers built on top of embedded HTTP servers such as GoAhead or boa derivatives.

Attack Vector

An attacker reaches the vulnerable endpoint over the network by sending a crafted HTTP POST request to /goform/aspApBasicConfigUrcp with an oversized Username value. The attack requires low-privilege authentication to the router's web interface. Successful exploitation can compromise confidentiality, integrity, and availability of the device, including persistent control of routing and DNS behavior on the network.

No verified exploitation code is reproduced here. Technical details and a proof-of-concept are documented in the GitHub CVE Documentation and the VulDB #316269 entry.

Detection Methods for CVE-2025-7571

Indicators of Compromise

HTTP POST requests to /goform/aspApBasicConfigUrcp containing abnormally long Username values, typically exceeding several hundred bytes.
Unexpected reboots or crashes of the HiPER 840G web management service following inbound HTTP requests.
New or unexplained administrative sessions originating from external IP addresses against the router's management interface.

Detection Strategies

Inspect HTTP request bodies on traffic destined for the router management interface and alert on oversized form fields targeting goform endpoints.
Correlate web management authentication events with subsequent device reboots or service restarts to identify exploitation attempts.
Use network intrusion detection signatures that flag long Username parameters posted to aspApBasicConfigUrcp.

Monitoring Recommendations

Forward router syslog and HTTP access logs to a centralized log platform and retain them for retrospective hunting.
Track configuration changes on the HiPER 840G and alert on modifications outside approved change windows.
Monitor for unexpected external connectivity to the router's web management port, which should not be reachable from the internet.

How to Mitigate CVE-2025-7571

Immediate Actions Required

Restrict access to the router's web management interface to a dedicated management VLAN or trusted administrator hosts only.
Disable WAN-side access to the HTTP and HTTPS management services on affected HiPER 840G devices.
Rotate all administrator credentials and review account inventory for unauthorized low-privilege accounts that could reach the vulnerable endpoint.
Evaluate replacement of end-of-life UTT HiPER 840G hardware where the vendor has not issued a patch.

Patch Information

UTT has not published a security advisory or firmware update addressing CVE-2025-7571 at the time of disclosure. The vendor did not respond to coordinated disclosure attempts according to the VulDB #316269 CTI record. Operators should monitor the UTT product portal for future firmware releases referencing aspApBasicConfigUrcp or the Username parameter fix.

Workarounds

Place the router's management interface behind a network access control list that allows only specified administrator IP addresses.
Terminate any unused or default low-privilege accounts to remove the authentication context required for exploitation.
Front the management interface with a reverse proxy or WAF that enforces a maximum length on the Username form parameter.
Where feasible, migrate critical network segments to a supported router platform that receives active security updates.

bash

# Example: restrict management access with an upstream firewall rule
# Allow only the admin workstation to reach the router web UI
iptables -A FORWARD -s 10.10.20.5/32 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP