CVE-2026-105821: Broken Access Control Leading to Cross-Device Token Issuance in Tapo Cloud MQTT Proxy

The Tapo Cloud MQTT broker contains a broken access control vulnerability in a proxy topic used by authenticated Tapo devices to request service tokens. The broker does not verify that the device ID supplied in a proxy request belongs to the authenticated device. An attacker who owns a Tapo device and knows another device's ID may obtain a device token scoped to the target device and use it to upload attacker-controlled content to the target user's Tapo Cloud storage. The content may then be presented in the Tapo app as a legitimate event.

Successful exploitation may allow an attacker to upload attacker-controlled content that is presented to a target user as a legitimate Tapo event, retrieve internal service information through crafted proxy requests, or abuse Tapo Cloud outbound request capability in activity that could affect service availability.