An improper handling of exceptional conditions vulnerability exists in the DNS proxy feature of Palo Alto Networks PAN-OS software that enables a meddler-in-the-middle (MITM) to send specifically crafted traffic to the firewall that causes the service to restart unexpectedly. Repeated attempts to send this request result in denial-of-service to all PAN-OS services by restarting the device in maintenance mode. This issue does not impact Panorama appliances and Prisma Access customers. This issue impacts: PAN-OS 8.1 versions earlier than PAN-OS 8.1.22; PAN-OS 9.0 versions earlier than PAN-OS 9.0.16; PAN-OS 9.1 versions earlier than PAN-OS 9.1.13; PAN-OS 10.0 versions earlier than PAN-OS 10.0.10; PAN-OS 10.1 versions earlier than PAN-OS 10.1.5. This issue does not impact PAN-OS 10.2.