Totolink A7100RU cstecgi.cgi setFirewallType (os command injection)

The Command Injection vulnerability in the Totolink A7100RU router allows an attacker to execute arbitrary commands on the device. This means an attacker could potentially gain full control of the router, including the ability to modify configurations, access sensitive data (such as user credentials and network traffic logs), and launch attacks against other devices on the network. The remote nature of the exploit significantly increases the attack surface, as it can be triggered from anywhere with network access to the router. Successful exploitation could lead to data breaches, denial-of-service attacks, and the use of the router as a pivot point for further attacks within the network.

Small and medium-sized businesses (SMBs) and home users relying on the Totolink A7100RU router are at significant risk. Shared hosting environments where multiple users share the same router infrastructure are particularly vulnerable, as a compromise of one user's router could potentially impact others. Users with default router configurations or weak passwords are also at increased risk.

• linux / server:

journalctl -u cstecgi -g 'command injection'

• generic web:

curl -s -X POST 'http://<router_ip>/cgi-bin/cstecgi.cgi?firewallType=;id;ls' | grep 'ls'

1. 2026-04-06Disclosure

   disclosure

1. Reserviert2026-04-06
2. Veröffentlicht2026-04-06
3. Geändert2026-04-07
4. EPSS aktualisiert2026-04-14

Due to the absence of a direct firmware patch, mitigation strategies for CVE-2026-5691 focus on reducing the attack surface and detecting malicious activity. Implement a Web Application Firewall (WAF) or reverse proxy to filter incoming traffic and block requests containing suspicious patterns in the firewallType parameter. Restrict access to the /cgi-bin/cstecgi.cgi endpoint using firewall rules, allowing only trusted IP addresses. Monitor router logs for unusual command execution attempts. Consider temporarily disabling the affected functionality if possible. After implementing these mitigations, verify their effectiveness by attempting to trigger the vulnerability with a controlled payload and confirming that the command is blocked.