CVE-2024-7176: Totolink A3600R Buffer Overflow Flaw

CVE-2024-7176 Overview

CVE-2024-7176 is a buffer overflow vulnerability in TOTOLINK A3600R routers running firmware version 4.1.2cu.5182_B20201102. The flaw resides in the setIpQosRules function of /cgi-bin/cstecgi.cgi, where the comment argument is copied into a fixed-size buffer without proper length validation. Attackers can trigger the overflow remotely over the network. Public exploit details were disclosed under identifier VDB-272597, and the vendor did not respond to disclosure attempts. The weakness is classified under CWE-120: Buffer Copy without Checking Size of Input.

Critical Impact
Remote attackers with low privileges can corrupt memory on affected TOTOLINK A3600R devices, potentially achieving arbitrary code execution and full router compromise.

Affected Products

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

Discovery Timeline

2024-07-29 - CVE-2024-7176 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-7176

Vulnerability Analysis

The TOTOLINK A3600R exposes a CGI binary named cstecgi.cgi that processes router configuration requests. The setIpQosRules handler accepts a comment parameter used to label Quality of Service rules. This parameter is copied into a stack or heap buffer of fixed size without bounds checking. Supplying a comment value longer than the destination buffer overwrites adjacent memory. Because MIPS-based TOTOLINK firmware typically lacks modern exploit mitigations such as consistent Address Space Layout Randomization (ASLR) and stack canaries, memory corruption at this location can be steered toward arbitrary code execution on the router.

Root Cause

The root cause is missing input validation on the comment argument before it is written to a fixed-size buffer, matching [CWE-120]. The handler trusts attacker-controlled length data rather than enforcing a maximum size or using bounded string copy routines. Combined with the CGI endpoint's authenticated but low-privilege access model, the flaw allows a low-privileged user to reach vulnerable code inside the router's HTTP management service.

Attack Vector

Exploitation occurs over the network by sending a crafted HTTP POST request to /cgi-bin/cstecgi.cgi invoking the setIpQosRules function with an oversized comment field. The attacker needs low-level authenticated access to reach the endpoint, and the request contains a payload sized to overflow the destination buffer. See the public vulnerability writeup on GitHub and VulDB entry #272597 for technical details.

// No verified exploit code is included.
// See the referenced GitHub advisory for reproduction details.

Detection Methods for CVE-2024-7176

Indicators of Compromise

HTTP POST requests to /cgi-bin/cstecgi.cgi containing the setIpQosRules action with unusually long comment values
Unexpected reboots, crashes, or watchdog resets on TOTOLINK A3600R devices
New administrative sessions or configuration changes on the router originating from unfamiliar source IP addresses
Outbound connections initiated by the router to unknown hosts, indicating possible post-exploitation implants

Detection Strategies

Inspect HTTP request bodies destined for the router management interface and flag comment field lengths that exceed reasonable limits (for example, more than 128 bytes)
Alert on any exposure of TOTOLINK A3600R management interfaces to WAN or untrusted VLANs
Correlate router syslog reboot events with preceding HTTP traffic to cstecgi.cgi

Monitoring Recommendations

Forward router syslog and web administration logs to a central log platform for retention and search
Monitor DNS and NetFlow telemetry from the router's management IP for anomalous outbound activity
Track firmware versions across the fleet and alert when devices remain on 4.1.2cu.5182_B20201102

How to Mitigate CVE-2024-7176

Immediate Actions Required

Remove TOTOLINK A3600R management interfaces from the internet and any untrusted network segments
Restrict access to /cgi-bin/cstecgi.cgi to a dedicated management VLAN and specific administrator IP addresses
Rotate router administrator credentials and disable any unused local accounts
Evaluate replacement of the A3600R with a supported device, given the vendor's lack of response to disclosure

Patch Information

No vendor patch is available. Per the NVD entry, TOTOLINK was contacted about this disclosure but did not respond. Organizations should track the VulDB record for CVE-2024-7176 for any future vendor updates and treat the device as end-of-support until a fix is published.

Workarounds

Disable remote management on the WAN interface and require LAN-side access for administration
Place affected routers behind an upstream firewall that blocks inbound HTTP and HTTPS to the router's management port
Segment IoT and networking equipment away from user and server networks to limit blast radius if the router is compromised
Replace affected TOTOLINK A3600R units with actively supported hardware where feasible

bash

# Example: block external access to the router management interface
# Adjust ROUTER_IP and MGMT_PORT for your environment
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 80 -i <WAN_IF> -j DROP
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 443 -i <WAN_IF> -j DROP