A NULL pointer dereference in D-Link DAP-1513 REVA_FIRMWARE_1.01 allows attackers to cause a Denial of Service (DoS) via a crafted web request without authentication. The vulnerability occurs in the /bin/webs binary of the firmware. When /bin/webs receives a carefully constructed HTTP request, it will crash and exit due to a null pointer reference, leading to a denial of service attack to the device.
A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.