Siemens SCALANCE X Switches (Update B)

1. EXECUTIVE SUMMARY

• CVSS v3 8.8
• ATTENTION: Exploitable remotely/low attack complexity
• Vendor: Siemens
• Equipment: SCALANCE X Switches
• Vulnerability: Missing Authentication for Critical Function

2. UPDATE INFORMATION

This updated advisory is a follow-up to the original advisory titled ICSA-20-014-03 Siemens SCALANCE X Switches (Update A) that was published February 10, 2021, to the ICS webpage on www.cisa.gov/uscert.

3. RISK EVALUATION

Successful exploitation of this vulnerability could allow an unauthenticated attacker to violate access-control rules.

4. TECHNICAL DETAILS

4.1 AFFECTED PRODUCTS

The following versions of SCALANCE X Switches, used to connect industrial components, are affected:

--------- Begin Update B Part 1 of 2 ---------

• SCALANCE X-200RNA (HSA): All versions prior to v3.2.7
• SCALANCE X-200RNA (PRP): All versions prior to v3.2.7
• SCALANCE X-200RNA EEC (HSR): All versions prior to v3.2.7
• SCALANCE X-200RNA EEC (PRP): All versions prior to v3.2.7

--------- End Update B Part 1 of 2 ---------

• SCALANCE X-300 switch family (incl. X408 and SIPLUS NET variants): All versions prior to v4.1.3

4.2.1    MISSING AUTHENTICATION FOR CRITICAL FUNCTION CWE-306

This vulnerability could be exploited by an attacker with network access to the affected systems. An attacker could obtain sensitive information or change the device configuration.

CVE-2019-13933 has been assigned to this vulnerability. A CVSS v3 base score of 8.8 has been assigned; the CVSS vector string is (AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L).

4.3 BACKGROUND

• CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing
• COUNTRIES/AREAS DEPLOYED: Worldwide
• COMPANY HEADQUARTERS LOCATION: Germany

4.4 RESEARCHER

Maxim Rupp reported this vulnerability to Siemens.

5. MITIGATIONS

Siemens recommends the following workarounds and mitigations affected users can apply to reduce risk:

--------- Begin Update B Part 2 of 2 ---------

• SCALANCE X-200RNA (HSA): Update to v3.2.7 or later
• SCALANCE X-200RNA (PRP): Update to v3.2.7 or later
• SCALANCE X-200RNA EEC (HSR): Update to v3.2.7 or later
• SCALANCE X-200RNA EEC (PRP): Update to v3.2.7 or later

--------- End Update B Part 2 of 2 ---------

• For the SCALANCE X-300 switch family (including X408 and SIPLUS NET variants) it is recommended that users upgrade to Version 4.1.3

Siemens has identified the following specific workarounds and mitigations that customers can apply to reduce the risk:

• Configure ACLs to only allow Web-based management from trusted IP addresses.
• Disable web-based management (WBM) and use SSH to configure the device.

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 Siemens Security Advisory SSA-443566

CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability. Specifically, users should:

• Minimize network exposure for all control system devices and/or systems, and ensure 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.

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/ics Several recommended practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.

Additional mitigation guidance and recommended practices are publicly available on the ICS webpage on cisa.gov/ics 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.

No known public exploits specifically target this vulnerability.