A stack overflow vulnerability exists in Totolink A7000R firmware version 9.1.0u.6115_B20201022 via the wifiOff parameter in the sub_421A04 function. This flaw can be exploited by an attacker sending a crafted request to cause a Denial of Service (DoS) condition. The vulnerability has a high severity score of 7.5 and does not affect confidentiality or integrity, only availability.