Juniper Junos before 11.4R11, 12.1 before 12.1R9, 12.2 before 12.2R7, 12.3R4 before 12.3R4-S3, 13.1 before 13.1R4, 13.2 before 13.2R2, and 13.3 before 13.3R1, as used in MX Series and T4000 routers, allows remote attackers to cause a denial of service (PFE restart) via a crafted IP packet to certain (1) Trio or (2) Cassis-based Packet Forwarding Engine (PFE) modules.