A critical security vulnerability has been identified in Tenda AC18 firmware version 15.03.05.19. The flaw resides in the /goform/telnet endpoint within the Telnet Handler component. The vulnerability allows attackers to bypass authentication entirely, enabling unauthorized remote access. The attack vector is network-based and requires no authentication or special privileges. A public exploit has already been released, significantly raising the risk of active exploitation. The vulnerability is classified as missing authentication, which is a fundamental security control failure. Affected users should apply patches or mitigations as soon as possible to prevent unauthorized access to their routers.