Cisco IOS XE before 3.1.2S on ASR 1000 devices mishandles the automatic setup of Virtual Fragment Reassembly (VFR) by certain firewall and NAT components, which allows remote attackers to cause a denial of service (Embedded Services Processor crash) via crafted IP packets, aka Bug IDs CSCtf87624, CSCte93229, CSCtd19103, and CSCti63623.