The U‑SPEED AC1200 Gigabit Wi‑Fi Router (Model T18‑21K) V1.0 contains an Unauthorized Access Control flaw that allows an attacker with physical access to its UART pins to directly interact with the device. The UART interface lacks authentication, authorization, or other access‑control checks, giving the attacker full control of device operations. This flaw can lead to complete device compromise and unauthorized use of the router’s functions. Based strictly on the provided description, the vulnerability is a classic CWE‑284 incorrect access control.

Devices matching the U‑SPEED AC1200 Gigabit Wi‑Fi Router (Model: T18‑21K) V1.0 are affected. No additional vendor or product information is available, and no detailed affected‑version list is provided.

The CVSS score is not provided, but the flaw grants unrestricted device functionality to anyone with physical access, indicating a high severity. The EPSS is not available and the vulnerability is not listed in CISA KEV. Because the UART interface does not enforce any authentication or authorization, the attack can be executed directly by plugging a serial cable into the pins, without requiring network access or remote exploits. The main prerequisite is physical proximity to the device, giving an attacker the capability to send arbitrary commands or modify firmware if desired.