CVE-2024-7184: Totolink A3600R Buffer Overflow Vulnerability

CVE-2024-7184 Overview

CVE-2024-7184 is a buffer overflow vulnerability in the TOTOLINK A3600R router running firmware version 4.1.2cu.5182_B20201102. The flaw resides in the setUrlFilterRules function within /cgi-bin/cstecgi.cgi, where the url argument is not properly bounds-checked. Remote attackers with low privileges can supply an oversized url parameter to corrupt memory on the device. The exploit has been publicly disclosed, and the vendor did not respond to disclosure attempts. The vulnerability is classified under [CWE-120] (Buffer Copy without Checking Size of Input).

Critical Impact
Remote attackers can trigger buffer corruption in the router's HTTP CGI handler, potentially leading to arbitrary code execution or full device compromise over the network.

Affected Products

TOTOLINK A3600R hardware
TOTOLINK A3600R firmware 4.1.2cu.5182_B20201102
Devices running the vulnerable cstecgi.cgi binary exposing setUrlFilterRules

Discovery Timeline

2024-07-29 - CVE-2024-7184 published to NVD with public disclosure via VulDB (VDB-272605)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-7184

Vulnerability Analysis

The vulnerability exists in the setUrlFilterRules handler implemented in /cgi-bin/cstecgi.cgi, a binary responsible for processing router administration requests on the TOTOLINK A3600R. When the handler receives an HTTP request containing a url parameter, it copies the attacker-supplied string into a fixed-size stack buffer without validating its length. Supplying an oversized value overwrites adjacent stack memory, including saved return addresses and control data.

Successful exploitation compromises the confidentiality, integrity, and availability of the device. On MIPS-based SOHO routers such as the A3600R, this class of stack-based overflow is commonly weaponized into arbitrary code execution using ROP gadgets, given the absence of mitigations such as ASLR and stack canaries in the firmware.

Root Cause

The root cause is missing input length validation in the setUrlFilterRules function before copying the user-controlled url argument into a local buffer. The code path uses an unbounded string copy operation on data taken directly from the HTTP request, satisfying the definition of [CWE-120].

Attack Vector

The vulnerability is network-reachable through the router's web management interface. An authenticated attacker with low privileges can send a crafted HTTP POST request to /cgi-bin/cstecgi.cgi invoking setUrlFilterRules with an overlong url value. No user interaction is required, and the attack complexity is low. If the management interface is exposed to the WAN, attackers can reach the endpoint directly from the internet.

A public write-up describing the exploitation path is available in the GitHub IoT vulnerability repository.

Detection Methods for CVE-2024-7184

Indicators of Compromise

HTTP requests to /cgi-bin/cstecgi.cgi containing setUrlFilterRules with abnormally long url parameter values
Router crashes, spontaneous reboots, or httpd/cstecgi process restarts correlated with inbound admin traffic
Unexpected outbound connections from the router to attacker-controlled hosts following management-interface activity
New or altered URL filter rules that were not created by an administrator

Detection Strategies

Inspect network traffic destined for the router management interface for oversized query strings or POST bodies targeting cstecgi.cgi
Alert on repeated POST requests to /cgi-bin/cstecgi.cgi from a single source within a short interval
Correlate router syslog entries indicating segmentation faults or watchdog resets with contemporaneous HTTP activity

Monitoring Recommendations

Forward router logs to a centralized SIEM or data lake for retention and correlation with other network telemetry
Monitor DNS and NetFlow data for anomalous egress from the router itself, which typically should not initiate outbound sessions to arbitrary hosts
Track firmware version inventory across deployed TOTOLINK devices to identify systems still running 4.1.2cu.5182_B20201102

How to Mitigate CVE-2024-7184

Immediate Actions Required

Disable remote (WAN-side) administration on the TOTOLINK A3600R and restrict the web management interface to trusted LAN segments only
Change default administrator credentials and enforce strong passwords to raise the bar for the required low-privilege access
Segment the router's management VLAN from user and IoT networks to limit lateral reach if the device is compromised
Consider replacing the device if it is deployed in a sensitive environment, given the vendor's lack of response to the disclosure

Patch Information

No vendor patch is available. According to the disclosure record, the vendor was contacted early but did not respond. Organizations should treat the device as unpatched and rely on compensating controls, or migrate to a supported router platform.

Workarounds

Block external access to TCP ports used by the router's web administration interface at the upstream firewall
Place an ACL in front of the router that permits management traffic only from designated administrative hosts
Remove or disable URL filter functionality where operationally feasible to reduce exposure of the affected handler
Retire the affected firmware version by upgrading to a maintained OpenWrt build (where supported) or replacing the hardware

bash

# Example: restrict router admin interface to a management subnet using iptables on an upstream gateway
iptables -A FORWARD -s 10.10.0.0/24 -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