1. EXECUTIVE SUMMARY

  • CVSS v3 6.5
  • ATTENTION: Low attack complexity
  • Vendor: Siemens
  • Equipment: RWG Universal Controllers
  • Vulnerability: Allocation of Resources Without Limits or Throttling

2. RISK EVALUATION

Successful exploitation of this vulnerability could allow an attacker to cause a denial-of-service condition.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

Siemens reports this vulnerability affects the following RWG controllers:

  • RWG1.M8: All versions prior to v1.16.16
  • RWG1.M12: All versions prior to v1.16.16
  • RWG1.M12D: All versions prior to v1.16.16

3.2 VULNERABILITY OVERVIEW

3.2.1    ALLOCATION OF RESOURCES WITHOUT LIMITS OR THROTTLING CWE-770
Sending specially crafted ARP packets to an affected device could cause a partial denial-of-service, which may prevent the device from operating normally. A restart is needed to restore normal operations.
CVE-2021-25671 has been assigned to this vulnerability. A CVSS v3 base score of 6.5 has been calculated; the CVSS vector string is (AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

3.3 BACKGROUND

  • CRITICAL INFRASTRUCTURE SECTORS: Chemical, Critical Manufacturing, Energy, Food and Agriculture, Water and Wastewater Systems
  • COUNTRIES/AREAS DEPLOYED: Worldwide
  • COMPANY HEADQUARTERS LOCATION: Germany

3.4 RESEARCHER

Siemens reported this vulnerability to CISA.

4. MITIGATIONS

Siemens recommends users login to the RWG Controller Graphical programming platform, generate a new project file, and download the new project file to the device.


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

  • Ensure only trusted systems are connected to the same Layer 2 domain as the affected devices;
  • Restrict access to systems in the same Layer 2 domain as the affected devices to trusted persons only.

As a general security measure, Siemens strongly 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 the recommendations in the product manuals.
Additional information on industrial security by Siemens can be found at: https://www.siemens.com/industrialsecurity.
Please see Siemens Security Advisory SSA-448291 for more information.

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 that VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize that VPN is 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 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. This vulnerability is not exploitable remotely.

Source:

https://us-cert.cisa.gov/ics/advisories/icsa-21-194-14