A vulnerability was discovered in Siemens SIMATIC Logon (All versions before V1.6) that could allow specially crafted packets sent to the SIMATIC Logon Remote Access service on port 16389/tcp to cause a Denial-of-Service condition. The service restarts automatically.
https://www.tenable.com/security/research/tra-2017-34
https://www.siemens.com/cert/pool/cert/siemens_security_advisory_ssa-804859.pdf