BIG-IP LTM, AAM, AFM, Analytics, APM, ASM, Link Controller, and PEM 12.0.0 before HF1, when the TCP profile for a virtual server is configured with Congestion Metrics Cache enabled, allow remote attackers to cause a denial of service (Traffic Management Microkernel (TMM) restart) via crafted ICMP packets, related to Path MTU (PMTU) discovery.