CVE-2026-6194 Overview
CVE-2026-6194 is a stack-based buffer overflow vulnerability in the Totolink A3002MU router running firmware version B20211125.1046. The flaw resides in the sub_410188 function within the /boafrm/formWlanSetup endpoint, part of the device's HTTP Request Handler component. Attackers manipulate the wan-url argument to trigger the overflow remotely. A public exploit exists, increasing the risk of opportunistic attacks against exposed devices. The vulnerability is categorized under [CWE-119], improper restriction of operations within the bounds of a memory buffer.
Critical Impact
Remote attackers with low privileges can corrupt stack memory through the wan-url parameter, potentially achieving code execution or denial of service on affected Totolink A3002MU routers.
Affected Products
- Totolink A3002MU router
- Firmware version B20211125.1046
- HTTP Request Handler component (/boafrm/formWlanSetup)
Discovery Timeline
- 2026-04-13 - CVE-2026-6194 published to NVD
- 2026-04-22 - Last updated in NVD database
Technical Details for CVE-2026-6194
Vulnerability Analysis
The vulnerability affects the sub_410188 function that processes HTTP requests sent to /boafrm/formWlanSetup on the Totolink A3002MU router. The function handles the wan-url parameter without enforcing proper length validation before copying user-supplied data into a fixed-size stack buffer. An oversized value submitted in this parameter overflows the buffer and overwrites adjacent stack memory, including saved registers and return addresses.
The attack is remotely exploitable over the network and requires only low privileges. Successful exploitation impacts confidentiality, integrity, and availability of the device. Because the public exploit is already available, defenders should treat any internet-facing Totolink A3002MU as at immediate risk.
Root Cause
The root cause is the absence of bounds checking when sub_410188 copies the attacker-controlled wan-url string into a stack-allocated buffer. Common patterns leading to this class of bug include use of unchecked string operations such as strcpy or sprintf against attacker-controlled input. The flaw maps to [CWE-119], improper restriction of operations within memory buffer bounds.
Attack Vector
An authenticated attacker sends a crafted HTTP POST request to the /boafrm/formWlanSetup endpoint with an oversized wan-url parameter. The request reaches the vulnerable sub_410188 handler in the boa-derived web server. The overflow corrupts the saved return address, allowing the attacker to redirect execution. On MIPS-based embedded devices without modern memory protections, this can lead to arbitrary code execution at the privilege level of the web server process.
The vulnerability is documented in the GitHub Vulnerability Report and tracked as VulDB #357116. No verified exploit code is reproduced here; refer to the public report for technical details.
Detection Methods for CVE-2026-6194
Indicators of Compromise
- Unusually large HTTP POST requests targeting /boafrm/formWlanSetup on Totolink A3002MU devices.
- HTTP request bodies containing oversized or non-printable byte sequences in the wan-url parameter.
- Web server crashes, restarts, or unexpected reboots on affected routers shortly after inbound HTTP traffic.
- Outbound connections from the router to unfamiliar hosts following suspicious inbound requests.
Detection Strategies
- Inspect HTTP traffic destined for the router's management interface and alert on requests to /boafrm/formWlanSetup exceeding expected parameter lengths.
- Deploy network IDS signatures matching wan-url parameter values longer than the legitimate maximum URL length.
- Correlate router crash or reboot events with preceding HTTP traffic from external sources.
Monitoring Recommendations
- Restrict and monitor exposure of the router web management interface to the public internet.
- Log all administrative HTTP requests at a network egress point for retrospective analysis.
- Review router syslog output for repeated boa web server failures indicating exploitation attempts.
How to Mitigate CVE-2026-6194
Immediate Actions Required
- Disable WAN-side access to the router's HTTP administration interface and limit management to trusted internal networks.
- Place affected Totolink A3002MU devices behind a firewall that filters unsolicited inbound HTTP traffic.
- Audit router accounts and rotate administrative credentials, since low-privileged authentication is sufficient for exploitation.
- Monitor the Totolink Official Website for firmware updates addressing this issue.
Patch Information
At the time of CVE publication, no vendor patch has been confirmed in the available references. Tracking continues through VulDB #357116 and the VulDB CTI #357116 entry. Administrators should consult Totolink directly for firmware availability superseding B20211125.1046.
Workarounds
- Block external access to TCP port 80 and any HTTPS management port on the router at the upstream firewall.
- Disable remote management features so the /boafrm/formWlanSetup endpoint is not reachable from the WAN interface.
- Segment the router's management VLAN from general user networks to limit attacker reachability.
- Where feasible, replace end-of-support consumer routers with vendor-supported equipment that receives regular firmware updates.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
