SIMATIC S7-400 CPUs are affected by a security vulnerability which could lead to a Denial-of-Service condition of the PLC if specially crafted packets are received and processed.
The affected SIMATIC S7-400 CPU hardware versions are in the product cancellation phase or already phased-out. Siemens recommends customers either upgrading to a new version or implementing specific countermeasures.
As a general security measure, Siemens strongly recommends to protect network access to devices with appropriate mechanisms. In order to operate the devices in a protected IT environment, Siemens recommends to configure the environment according to Siemens' operational guidelines for Industrial Security (Download: https://www.siemens.com/cert/operational-guidelines-industrial-security), and to follow the recommendations in the product manuals.
Additional information on Industrial Security by Siemens can be found at: https://www.siemens.com/industrialsecurity
Products in the SIMATIC S7-400 CPU family have been designed for process control in industrial environments. They are used worldwide, e.g. in the automotive industry, mechanical equipment manufacture, warehousing systems, building engineering, steel industry, power generation and distribution, pharmaceuticals, food and beverages industry, or chemical industry.
SIPLUS extreme products are designed for reliable operation under extreme conditions and are based on SIMATIC, LOGO!, SITOP, SINAMICS, SIMOTION, SCALANCE or other devices. SIPLUS devices use the same firmware as the product they are based on.
An additional classification has been performed using the CWE classification, a community-developed list of common software security weaknesses. This serves as a common language and as a baseline for weakness identification, mitigation, and prevention efforts. A detailed list of CWE classes can be found at: https://cwe.mitre.org/.
The affected CPUs improperly validate S7 communication packets which could cause a Denial-of-Service condition of the CPU. The CPU will remain in DEFECT mode until manual restart.
Successful exploitation requires an attacker to be able to send a specially crafted S7 communication packet to a communication interface of the CPU. This includes Ethernet, PROFIBUS, and Multi Point Interfaces (MPI). No user interaction or 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.
At the time of advisory publication no public exploitation of this security vulnerability was known. Siemens confirms the security vulnerability and provides mitigations to resolve the security issue.