Vulnerabilities in Nucleus RTOS from Siemens

November 10, 2021 - Researchers from cybersecurity company Forescout and Medigate, a firm that focuses on the security of devices for healthcare providers have provided details about a suite of 13 vulnerabilities affecting the Nucleus real-time operating system that supports devices in medical, industrial, automotive and aerospace sectors.

While there is no known public exploits specifically target these vulnerabilities, of those identified, three were remote code execution bugs that could allow the hackers to take control of the vulnerable device. U.S. Cybersecurity and Infrastructure Security Agency (CISA) also releases security advisory on siemens Nucleus RTOS by encouraging administrators and users to review ICSA-21-313-03 for information to mitigate these vulnerabilities.


Siemens provided the following mitigation guidance:

  1. Apply release updates as applicable. Siemens has released updates for several of the affected products and recommends updating to the latest versions. Siemens recommends countermeasures for products where updates are not available. Siemens has not identified any additional specific workarounds or mitigations.

  2. As a general security measure, Siemens recommends protecting network access to devices with appropriate mechanisms. In order to operate the devices in a protected IT environment, Siemens recommends configuring the environment according to Siemens’ operational guidelines for industrial security and following the recommendations in the product manuals.

CISA also provided the following additional mitigation guidance:

  1. CISA recommends users take defensive measures to minimize the risk of exploitation of these vulnerabilities. Specifically, users should:

  • Minimize network exposure for all control system devices and/or systems, and ensure that they are not accessible from the Internet.

  • Locate control system networks and remote devices behind firewalls, and isolate them from the business network.

  • When remote access is required, use secure methods, such as Virtual Private Networks (VPNs), recognizing VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize VPN is only as secure as its connected devices.

  1. CISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.

  2. CISA also provides a section for control systems security recommended practices on the ICS webpage on us-cert.cisa.gov. Several recommended practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.

  3. Survey additional mitigation guidance and recommended practices publicly available on the ICS webpage on us-cert.cisa.gov in the Technical Information Paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies.

Organizations observing any suspected malicious activity should follow their established internal procedures and report their findings to CISA for tracking and correlation against other incidents.