CVE-2026-93739: Totolink A3002MU Buffer Overflow Vulnerability

CVE-2026-93739 Overview

CVE-2026-93739 is a buffer overflow vulnerability in the Totolink A3002MU router running firmware version Hh-B20211125.1046. The flaw resides in the formWlAc function within the /boafrm/formWlAc endpoint. An attacker can trigger the overflow by manipulating the submit-url argument. The vulnerability is exploitable remotely over the network and requires only low privileges. The proof-of-concept has been publicly disclosed, increasing the likelihood of opportunistic exploitation against exposed devices. The weakness is classified under CWE-119, improper restriction of operations within the bounds of a memory buffer.

Critical Impact
Remote attackers with low-privilege access can corrupt memory in the router's web management interface, potentially achieving code execution or denial of service on affected Totolink A3002MU devices.

Affected Products

Totolink A3002MU router
Firmware version Hh-B20211125.1046
Web management interface handler /boafrm/formWlAc

Discovery Timeline

2026-09-18 - CVE-2026-93739 published to the National Vulnerability Database
2026-09-23 - Last updated in NVD database

Technical Details for CVE-2026-93739

Vulnerability Analysis

The vulnerability exists in the formWlAc handler exposed through the /boafrm/formWlAc URI of the Totolink A3002MU web administration interface. The handler processes wireless access control form submissions and reads user-supplied values, including the submit-url parameter, into a fixed-size stack buffer without validating input length. When an attacker submits an overly long submit-url value, the copy operation writes past the buffer boundary, corrupting adjacent stack memory. Successful exploitation can crash the boa HTTP daemon or, with crafted payloads targeting the MIPS/ARM binary layout, redirect execution flow. The public proof-of-concept demonstrates the overflow trigger against the vulnerable endpoint.

Root Cause

The root cause is missing bounds checking on the submit-url request parameter before it is copied into a stack-allocated buffer inside formWlAc. This is a classic CWE-119 failure to restrict a memory operation to the allocated buffer size. Totolink's firmware relies on unsafe string handling routines common to embedded boa-based web servers, where developer-side length validation is the only defense.

Attack Vector

Exploitation requires network reachability to the router's web interface and an authenticated session with low privileges. An attacker submits a crafted HTTP POST request to /boafrm/formWlAc with an oversized submit-url parameter. Because the interface is often exposed on the LAN, and in misconfigured deployments on the WAN, this vector is practical for internal attackers, malicious guests on Wi-Fi networks, or remote adversaries chasing exposed management panels. Refer to the GitHub proof-of-concept for A3002MU and the VulDB entry for CVE-2026-93739 for technical reproduction details.

Detection Methods for CVE-2026-93739

Indicators of Compromise

HTTP POST requests to /boafrm/formWlAc containing unusually long submit-url parameter values, particularly exceeding several hundred bytes.
Unexpected restarts or crashes of the boa web server process on the router.
Router web administration interface becoming unresponsive following a POST request to the affected endpoint.

Detection Strategies

Inspect network traffic between clients and router management interfaces for anomalous POST bodies targeting /boafrm/formWlAc.
Correlate router syslog messages showing daemon crashes with recent inbound HTTP requests to the wireless access control endpoint.
Deploy signatures on IDS/IPS platforms to flag oversized submit-url values sent to Totolink /boafrm/ handlers.

Monitoring Recommendations

Forward router logs to a centralized logging platform and alert on repeated boa process termination events.
Monitor for unauthorized changes to router configuration, firmware, or DNS settings that may follow successful exploitation.
Track authentication events on the router's administrative interface and alert on low-privilege accounts accessing configuration endpoints outside normal patterns.

How to Mitigate CVE-2026-93739

Immediate Actions Required

Restrict access to the router's web management interface to trusted management VLANs and block WAN-side administrative access.
Rotate all router administrative and low-privilege user credentials, and disable unused accounts that could be leveraged to reach the vulnerable endpoint.
Inventory Totolink A3002MU devices running firmware Hh-B20211125.1046 and prioritize them for replacement or firmware update.

Patch Information

At the time of publication, no vendor patch has been referenced in the enriched CVE data. Check the Totolink official website for firmware updates addressing the formWlAc handler, and review the VulDB vulnerability record #407549 for updates on remediation status.

Workarounds

Disable remote (WAN) management on the router and limit the web interface to a dedicated management subnet.
Place the router behind a network filter that blocks HTTP requests to /boafrm/formWlAc from untrusted sources.
If the device is end-of-life or unsupported, plan migration to a currently supported router platform that receives security updates.

bash

# Example firewall rule to restrict access to the router admin interface
# Replace 192.0.2.10 with your management workstation IP
# and 192.0.2.1 with the router's LAN address
iptables -A FORWARD -s 192.0.2.10 -d 192.0.2.1 -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -d 192.0.2.1 -p tcp --dport 80 -j DROP