Describe CVE-2018-16556.
What is CVE-2018-16556?
A vulnerability has been identified in  SIMATIC S7-400 CPU 412-1 DP V7 (All versions),  SIMATIC S7-400 CPU 412-2 DP V7 (All versions),  SIMATIC S7-400 CPU 414-2 DP V7 (All versions),  SIMATIC S7-400 CPU 414-3 DP V7 (All versions),  SIMATIC S7-400 CPU 414-3 PN/DP V7 (All versions < V7.0.3),  SIMATIC S7-400 CPU 414F-3 PN/DP V7 (All versions < V7.0.3),  SIMATIC S7-400 CPU 416-2 DP V7 (All versions),  SIMATIC S7-400 CPU 416-3 DP V7 (All versions),  SIMATIC S7-400 CPU 416-3 PN/DP V7 (All versions < V7.0.3),  SIMATIC S7-400 CPU 416F-2 DP V7 (All versions),  SIMATIC S7-400 CPU 416F-3 PN/DP V7 (All versions < V7.0.3),  SIMATIC S7-400 CPU 417-4 DP V7 (All versions), SIMATIC S7-400 CPU 412-2 PN V7 (All versions < V7.0.3), SIMATIC S7-400 H V4.5 and below CPU family (incl. SIPLUS variants) (All versions), SIMATIC S7-400 H V6 CPU family (incl. SIPLUS variants) (All versions < V6.0.9), SIMATIC S7-400 PN/DP V6 and below CPU family (incl. SIPLUS variants) (All versions), SIMATIC S7-410 CPU family (incl. SIPLUS variants) (All versions < V8.2.1), SIPLUS S7-400 CPU 414-3 PN/DP V7 (All versions < V7.0.3), SIPLUS S7-400 CPU 416-3 PN/DP V7 (All versions < V7.0.3), SIPLUS S7-400 CPU 416-3 V7 (All versions), SIPLUS S7-400 CPU 417-4 V7 (All versions). Specially crafted packets sent to port 102/tcp via Ethernet interface, via
PROFIBUS, or via Multi Point Interfaces (MPI) could cause the affected
devices to go into defect mode. Manual reboot is required to resume normal
operation.

Successful exploitation requires an attacker to be able to send specially
crafted packets to port 102/tcp via Ethernet interface, via PROFIBUS or Multi
Point Interfaces (MPI). No user interaction and no user privileges are
required to exploit the security vulnerability. The vulnerability could allow
causing a denial of service condition of the core functionality of the CPU,
compromising the availability of the system..