Executive brief
The Tenda AC18 wireless router contains an unauthenticated endpoint that enables telnet access. The router's factory-default configuration has an empty admin password, allowing an attacker on the network to remotely enable telnet without any credentials and gain command-line access to the device's management shell, potentially compromising the entire network infrastructure.
Technical details
The vulnerability is a missing authentication check (CWE-306) in the /goform/telnet HTTP handler within /bin/httpd. The default firmware configuration sets an empty sys.userpass value, and the telnet handler does not validate authentication before processing requests to enable telnetd. An unauthenticated, unauthenticated HTTP GET request to /goform/telnet triggers shell commands that start telnetd listening on the LAN IP without any login step, Cookie, or Authorization header required. This is a network-reachable pre-authentication vulnerability; an attacker can exploit it remotely from any network interface the router exposes. Once telnet is enabled, the attacker gains unauthenticated shell access to execute arbitrary commands on the device with root privileges.
Affected products
- Tenda AC18 15.03.05.19
Timeline
- 2026-08-31: disclosed
- exploited: Public exploit released