A null pointer dereference vulnerability in the GlobalProtect gateway in Palo Alto Networks PAN-OS software enables an unauthenticated attacker to stop the GlobalProtect service on the firewall by sending a specially crafted packet that causes a denial of service (DoS) condition. Repeated attempts to trigger this condition result in the firewall entering maintenance mode.
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.