The vulnerability is a classic buffer overflow (CWE‑120) in the addWewifiWhiteUser function of the Tenda W20E router. When a crafted userInfo string is processed by sscanf without size validation, the buffer is overflowed, corrupting adjacent memory. This can lead to arbitrary code execution or a denial‑of‑service condition on the device.

The flaw affects all Tenda W20E routers running firmware 4.0br V15.11.0.6.

The likely attack vector is remote via the router’s management interface that accepts the userInfo parameter, most plausibly a web or API endpoint. The CVSS score of 7.5 indicates high severity, while the EPSS score of less than 1% suggests that publicly documented exploitation is currently unlikely. The vulnerability is not listed in the CISA KEV catalog. An attacker does not need local or physical access; proximity to the device is therefore not required. Successful exploitation could grant code execution or force the router to reboot.