The vulnerability allows an attacker to manipulate the schedStartTime and schedEndTime parameters used by the setSchedWifi function on the Tenda A21 router. This causes a stack-based buffer overflow, which can be chained to execute arbitrary code and compromise the device entirely. The CVSS score of 8.7 indicates a high level of severity, and the public exploit can be delivered remotely by sending specially crafted requests.

Tenda A21 routers running firmware version 1.0.0.0. The flaw resides in the /goform/openSchedWifi endpoint of the device’s web interface.

Because the attack vector is remote, an adversary can reach the vulnerable endpoint from outside the local network. EPSS indicates a very low current exploitation probability, but the flaw is already publicly available and not listed in the CISA KEV catalog. If a patch is not applied, the risk of successful exploitation remains high, leading to full device compromise.