A stack-based buffer overflow exists in the GoAhead-Webs HTTP daemon on KuWFi 4G LTE AC900 devices with firmware 1.0.13. The /goform/formMultiApnSetting handler uses sprintf() to copy the user-supplied pincode parameter into a fixed 132-byte stack buffer with no bounds checks. This allows an attacker to corrupt adjacent stack memory, crash the web server, and (under certain conditions) may enable arbitrary code execution.