Siemens OPC UA Implementation in SINUMERIK ONE and SINUMERIK MC

As of January 10, 2023, CISA will no longer be updating ICS security advisories for Siemens product vulnerabilities beyond the initial advisory. For the most up-to-date information on vulnerabilities in this advisory, please see Siemens’ ProductCERT Security Advisories (CERT Services | Services | Siemens Global). View CSAF

1. EXECUTIVE SUMMARY CVSS v3 7.5 ATTENTION: Exploitable remotely/low attack complexity Vendor: Siemens Equipment: SINUMERIK MC, SINUMERIK ONE Vulnerability: Integer Overflow or Wraparound
2. RISK EVALUATION Successful exploitation of this vulnerability could allow an unauthenticated remote attacker to create a denial of service condition by sending a specially crafted certificate.
3. TECHNICAL DETAILS 3.1 AFFECTED PRODUCTS The following products of Siemens, are affected: SINUMERIK MC: All versions prior to V1.22 SINUMERIK ONE: All versions prior to V6.22 3.2 Vulnerability Overview 3.2.1 INTEGER OVERFLOW OR WRAPAROUND CWE-190 The OPC UA implementations (ANSI C and C++) in affected products contain an integer overflow vulnerability that could cause the application to run into an infinite loop during certificate validation. This could allow an unauthenticated remote attacker to create a denial-of-service condition by sending a specially crafted certificate. CVE-2023-28831 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). 3.3 BACKGROUND CRITICAL INFRASTRUCTURE SECTORS: Multiple COUNTRIES/AREAS DEPLOYED: Worldwide COMPANY HEADQUARTERS LOCATION: Germany 3.4 RESEARCHER Siemens reported this vulnerability to CISA.
4. MITIGATIONS Siemens has identified the following specific workarounds and mitigations users can apply to reduce risk: SINUMERIK MC: Expose the OPC UA interface of the integrated S7-1500 CPU only to trusted network environments Update to V1.22 or later version SINUMERIK ONE: Expose the OPC UA interface of the integrated S7-1500 CPU only to trusted network environments Update to V6.22 or later version As a general security measure, Siemens recommends protecting network access to devices with appropriate mechanisms. To operate the devices in a protected IT environment, Siemens recommends configuring the environment according to Siemens’ operational guidelines for industrial security and following recommendations in the product manuals. Additional information on industrial security by Siemens can be found on the Siemens industrial security webpage. For more information see the associated Siemens security advisory SSA-118850 in HTML and CSAF. CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability, such as: Minimize network exposure for all control system devices and/or systems, ensuring they are not accessible from the internet. Locate control system networks and remote devices behind firewalls and isolating them from business networks. When remote access is required, use more secure methods, such as Virtual Private Networks (VPNs). Recognize VPNs may have vulnerabilities, should be updated to the most recent version available, and are only as secure as the connected devices. CISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures. CISA also provides a section for control systems security recommended practices on the ICS webpage on cisa.gov. Several CISA products detailing cyber defense best practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies. CISA encourages organizations to implement recommended cybersecurity strategies for proactive defense of ICS assets. Additional mitigation guidance and recommended practices are publicly available on the ICS webpage at cisa.gov in the technical information paper, ICS-TIP-12-146-01B–Targeted Cyber Intrusion Detection and Mitigation Strategies. Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents. No known public exploitation specifically targeting this vulnerability has been reported to CISA at this time.
5. UPDATE HISTORY December 14, 2023: Initial Publication