Totolink A7100RU OS Command Injection Vulnerability (CVE-2026-6025)

A critical vulnerability, CVE-2026-6025, has been discovered in Totolink A7100RU router firmware version 7.4cu.2313_b20191024. This flaw resides within the CGI handler component, specifically in the setSyslogCfg function of the /cgi-bin/cstecgi.cgi file. Successful exploitation allows an unauthenticated, remote attacker to inject and execute arbitrary operating system commands on the affected device. The vulnerability is triggered by manipulating the enable argument. Given the availability of a public exploit, this poses a significant risk, potentially leading to widespread compromise of vulnerable Totolink routers. Exploitation requires no prior authentication, making it easily exploitable.

Attack Chain

1. An attacker identifies a vulnerable Totolink A7100RU router running firmware version 7.4cu.2313_b20191024.
2. The attacker crafts a malicious HTTP request targeting the /cgi-bin/cstecgi.cgi endpoint.
3. The attacker injects OS commands into the enable argument of the setSyslogCfg function within the HTTP request.
4. The router's CGI handler processes the request without proper sanitization of the enable argument.
5. The injected OS commands are executed with the privileges of the web server process.
6. The attacker gains initial access to the router's operating system.
7. The attacker may then escalate privileges, install persistent backdoors, or pivot to internal network resources.
8. The attacker achieves full control of the compromised router, potentially using it for botnet activities, data exfiltration, or denial-of-service attacks.

Impact

Successful exploitation of CVE-2026-6025 grants the attacker complete control over the compromised Totolink A7100RU router. This can lead to a variety of malicious activities, including botnet recruitment, data theft, and network disruption. Given the potential for widespread exploitation due to the public availability of an exploit, a large number of devices could be compromised, impacting both home and small business networks.

Recommendation

• Implement a web application firewall (WAF) rule to filter requests to /cgi-bin/cstecgi.cgi containing suspicious characters or command injection attempts in the enable parameter, based on analysis of exploit techniques.
• Monitor web server logs for unusual POST requests to /cgi-bin/cstecgi.cgi with abnormally long or encoded enable parameters to detect exploit attempts (see example rule below).
• Apply any available firmware updates from Totolink to patch CVE-2026-6025 on affected A7100RU routers, once released by the vendor.