ICSA-18-317-02: Siemens S7-400 CPUs (Update B)

CISA's summary

Summary: Two vulnerabilities have been identified in the SIMATIC S7-400 CPU family that could allow an attacker to cause a denial of service condition. In order to exploit the vulnerabilities, an attacker must have access to the affected devices on port 102/tcp via Ethernet, PROFIBUS or Multi Point Interfaces (MPI). Siemens has released updates for several affected products and recommends to update to the latest versions. Siemens recommends specific countermeasures for products where updates are not, or not yet available.

Products, as the advisory lists them

DeSpy has not checked any unit, hardware revision or firmware.

Vulnerabilities in this advisory

• CVE-2018-16556 — CVE-2018-16556 · CWE-20

  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-2018-16557 — CVE-2018-16557 · CWE-347

  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.

Acknowledgments, as the advisory lists them

• Siemens ProductCERT: reporting these vulnerabilities to CISA.

The advisory's legal notice

Siemens Security Advisories are subject to the terms and conditions contained in Siemens' underlying license terms or other applicable agreements previously agreed to with Siemens (hereinafter "License Terms"). To the extent applicable to information, software or documentation made available in or through a Siemens Security Advisory, the Terms of Use of Siemens' Global Website (https://www.siemens.com/terms_of_use, hereinafter "Terms of Use"), in particular Sections 8-10 of the Terms of Use, shall apply additionally. In case of conflicts, the License Terms shall prevail over the Terms of Use.

Sources

• The advisory at cisa.gov
• The CSAF document (JSON)

DeSpy's copy of this version is dated 2026-09-28.