Siemens SCALANCE XM-400 and XR-500 Devices

2021-05-11T00:00:00
ID ICSA-21-131-10
Type ics
Reporter Industrial Control Systems Cyber Emergency Response Team
Modified 2021-05-11T00:00:00

Description

1. EXECUTIVE SUMMARY

  • CVSS v3 7.5
  • ATTENTION: Exploitable remotely/low attack complexity
  • Vendor: Siemens
  • Equipment: SCALANCE XM-400, XR-500
  • Vulnerability: Incorrect Calculation

2. RISK EVALUATION

Successful exploitation of this vulnerability could allow an unauthenticated remote attacker to create a permanent denial-of-service condition.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following Siemens products are affected:

  • SCALANCE XM-400 Family: All versions prior to v6.4
  • SCALANCE XR-500 Family: All versions prior to v6.4

3.2 VULNERABILITY OVERVIEW

3.2.1 INCORRECT CALCULATION CWE-682

An unauthenticated remote attacker could create a permanent denial-of-service condition by sending specially crafted OSPF packets. Successful exploitation requires OSPF to be enabled on an affected device.

CVE-2020-28393 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

3.3 BACKGROUND

  • CRITICAL INFRASTRUCTURE SECTORS: Multiple Sectors
  • COUNTRIES/AREAS DEPLOYED: Worldwide
  • COMPANY HEADQUARTERS LOCATION: Germany

3.4 RESEARCHER

Siemens reported this vulnerability to CISA.

4. MITIGATIONS

Siemens recommends applying updates where available:

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

  • Disable OSPF in layer 3 configuration menu (note OSPF is disabled by default). This vulnerability is not exploitable, when OSPF is disabled.
  • If OSPF is used, set a password for the OSPF interface and enable MD5 authentication.

As a general security measure, Siemens strongly 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 the Siemens operational guidelines for Industrial Security and following the recommendations in the product manuals.

For additional information, please refer to Siemens Security Advisory SSA-116379

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 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.

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 us-cert.cisa.gov. 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 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.

No known public exploits specifically target this vulnerability.

Contact Information

For any questions related to this report, please contact the CISA at:

Email: CISAservicedesk@cisa.dhs.gov
Toll Free: 1-888-282-0870

For industrial control systems cybersecurity information: https://us-cert.cisa.gov/ics
or incident reporting: https://us-cert.cisa.gov/report

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