A vulnerability has been identified in SIMATIC S7-300 CPU family (All versions), SIMATIC S7-300 CPU family (incl. related ET200 CPUs and SIPLUS variants) (All versions), SIMATIC S7-400 PN/DP V6 and below CPU family (incl. SIPLUS variants) (All versions), SIMATIC S7-400 PN/DP V7 CPU family (incl. SIPLUS variants) (All versions), SIMATIC S7-400 V6 and earlier CPU family (All versions), SIMATIC S7-400 V7 CPU family (All versions). Specially crafted packets sent to port 80/tcp could cause the affected devices to go into defect mode. A cold restart is required to recover the system.
https://www.siemens.com/cert/pool/cert/siemens_security_advisory_ssa-731239.pdf
https://ics-cert.us-cert.gov/advisories/ICSA-16-348-05
https://cert-portal.siemens.com/productcert/pdf/ssa-731239.pdf