The kernel in Juniper Junos 10.4 before 10.4R14 11.4 before 11.4R8 11.4X27 before 11.4X27.43 12.1 before 12.1R6 12.1X44 before 12.1X44-D20 12.2 before 12.2R4 and 12.3 before 12.3R2 in certain VLAN configurations with unrestricted arp-resp and proxy-arp settings allows remote attackers to cause a denial of service (device crash) via a crafted ARP request aka PR 842091.