CVE-2024-7185: Totolink A3600r Buffer Overflow Vulnerability

CVE-2024-7185 Overview

CVE-2024-7185 is a buffer overflow vulnerability affecting the TOTOLINK A3600R router running firmware version 4.1.2cu.5182_B20201102. The flaw resides in the setWebWlanIdx function within /cgi-bin/cstecgi.cgi, where manipulation of the webWlanIdx argument triggers a stack-based buffer overflow [CWE-120]. Attackers can exploit this remotely over the network to compromise device confidentiality, integrity, and availability. The exploit has been publicly disclosed, increasing the risk of opportunistic attacks against exposed devices. The vendor was contacted about this disclosure but did not respond, leaving affected devices without a documented patch path.

Critical Impact
Remote attackers with low privileges can trigger memory corruption in the router's web management CGI, enabling potential code execution and full compromise of the affected TOTOLINK A3600R device.

Affected Products

TOTOLINK A3600R router (hardware)
TOTOLINK A3600R firmware version 4.1.2cu.5182_B20201102
Deployments exposing the /cgi-bin/cstecgi.cgi interface to untrusted networks

Discovery Timeline

2024-07-29 - CVE-2024-7185 published to NVD (VDB identifier VDB-272606)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-7185

Vulnerability Analysis

The vulnerability exists in the setWebWlanIdx handler exposed through the CGI binary /cgi-bin/cstecgi.cgi on the TOTOLINK A3600R. This handler processes the webWlanIdx HTTP request parameter without enforcing proper length validation before copying user-supplied data into a fixed-size buffer. The resulting stack corruption can overwrite adjacent memory, including saved return addresses and local variables used by the CGI process. Attackers reaching the management interface over the network can weaponize the overflow to crash the service or influence control flow on the embedded MIPS-based platform. Because the CGI runs with elevated privileges within the router firmware, successful exploitation grants meaningful control over the device.

Root Cause

The root cause is missing bounds checking on the webWlanIdx parameter within the setWebWlanIdx function. The firmware copies the attacker-controlled string into a fixed-length stack buffer using an unsafe string operation, classified under [CWE-120] (Buffer Copy Without Checking Size of Input). No input length validation or safe-copy primitive is applied prior to the copy.

Attack Vector

Exploitation requires network reachability to the router's web management service and a low level of privilege on the interface. An attacker sends a crafted HTTP request to /cgi-bin/cstecgi.cgi invoking setWebWlanIdx with an oversized webWlanIdx value. The malformed request corrupts the CGI process stack, resulting in denial of service or arbitrary code execution depending on payload construction. Public disclosure of the exploitation technique lowers the barrier for opportunistic attacks against internet-exposed devices.

No verified exploit code is reproduced here. Technical details are available in the GitHub IoT Vulnerability Overview and the VulDB CVE Analysis #272606.

Detection Methods for CVE-2024-7185

Indicators of Compromise

HTTP POST requests to /cgi-bin/cstecgi.cgi containing the setWebWlanIdx function selector with abnormally long webWlanIdx parameter values.
Repeated crashes, reboots, or unexpected restarts of the TOTOLINK A3600R web management daemon.
Outbound connections from the router to unfamiliar external hosts following suspicious CGI requests.

Detection Strategies

Monitor perimeter and internal traffic for HTTP requests targeting cstecgi.cgi with oversized query or POST body parameters, particularly webWlanIdx.
Deploy network intrusion detection signatures that flag parameter lengths exceeding expected wireless index values (typically single-digit integers).
Correlate router log anomalies, watchdog resets, and management interface disconnections with inbound HTTP traffic.

Monitoring Recommendations

Log and inspect all administrative HTTP requests reaching TOTOLINK devices, especially from non-management VLANs.
Alert on any unauthenticated or unexpected external access to the router's HTTP interface.
Track firmware version inventory to identify assets running 4.1.2cu.5182_B20201102 or earlier vulnerable builds.

How to Mitigate CVE-2024-7185

Immediate Actions Required

Restrict access to the router's web administration interface to trusted management networks only, blocking WAN-side exposure.
Change default and weak administrative credentials to reduce the pool of low-privilege attackers able to reach the vulnerable endpoint.
Segment IoT and networking equipment from user and server VLANs to contain potential compromise.
Consider replacing the TOTOLINK A3600R with a supported device in high-risk deployments, given the absence of a vendor response.

Patch Information

No vendor patch has been published. According to the disclosure record, TOTOLINK was contacted about the issue but did not respond. Administrators should monitor the VulDB entry #272606 and TOTOLINK support channels for any future firmware updates addressing the setWebWlanIdx handler.

Workarounds

Disable remote (WAN) management on the A3600R and permit LAN-side administration only from designated workstations.
Place an upstream firewall or ACL in front of the router to filter inbound HTTP requests to /cgi-bin/cstecgi.cgi.
Deploy an inline IDS/IPS rule that drops HTTP requests containing an oversized webWlanIdx parameter to cstecgi.cgi.
Where feasible, retire vulnerable firmware and migrate to a currently supported router platform.

bash

# Example iptables rule restricting router HTTP management to a trusted subnet
iptables -A INPUT -p tcp --dport 80 -s 10.0.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 10.0.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP