Siemens S7-400 CPUs (Update B)
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. CVE-2018-16556 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). Sending of specially crafted packets to port 102/tcp via Ethernet interface
via PROFIBUS or Multi Point Interfaces (MPI) could cause a denial of service
condition on affected devices. Flashing with a firmware image may be required
to recover the CPU.

Successful exploitation requires an attacker to have network access to port
102/tcp via Ethernet interface or to be able to send messages via PROFIBUS or
Multi Point Interfaces (MPI) to the device. No user interaction is required.
If no access protection is configured, no 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. CVE-2018-16557 has been assigned to this vulnerability. A CVSS v3 base score of 8.2 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H).