Siemens SIMATIC NET CP Modules

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).

1. EXECUTIVE SUMMARY

• CVSS v3 7.5
• ATTENTION: Exploitable remotely/low attack complexity
• Vendor: Siemens
• Equipment: SIMATIC CP 343-1 (incl. SIPLUS variants), SIMATIC CP 343-1 Advanced (incl. SIPLUS variants), SIMATIC CP 343-1 ERPC, SIMATIC CP 343-1 Lean (incl. SIPLUS variants), SIMATIC CP 443-1 (incl. SIPLUS variants), SIMATIC CP 443-1 Advanced (incl. SIPLUS variants)
• Vulnerability: Improper Restriction of Operations within the Bounds of a Memory Buffer

2. RISK EVALUATION

Successful exploitation of this vulnerability could allow an attacker to cause the device to become unavailable until the device is restarted.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following versions of SIMATIC NET CP Modules, a communication processor, are affected:

• SIMATIC CP 343-1 (incl. SIPLUS variants) all versions
• SIMATIC CP 343-1 Advanced (incl. SIPLUS variants) all versions
• SIMATIC CP 343-1 ERPC all versions
• SIMATIC CP 343-1 Lean (incl. SIPLUS variants) all versions
• SIMATIC CP 443-1 (incl. SIPLUS variants) all versions
• SIMATIC CP 443-1 Advanced (incl. SIPLUS variants) all versions

3.2 VULNERABILITY OVERVIEW

3.2.1    IMPROPER RESTRICTION OF OPERATIONS WITHIN THE BOUNDS OF A MEMORY BUFFER CWE-119

Sending a specially crafted packet to Port 102/TCP of an affected device could cause a denial-of-service condition. A restart is needed to restore normal operations.

CVE-2021-33737 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: Critical Manufacturing
• COUNTRIES/AREAS DEPLOYED: Worldwide
• COMPANY HEADQUARTERS LOCATION: Germany

3.4 RESEARCHER

Michael Messner from Siemens Energy reported this vulnerability to Siemens.

4. MITIGATIONS

Siemens recommends affected users limit access to Port 102/TCP to trusted users and systems only.

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 Siemens’ operational guidelines for industrial security and to following the recommendations in the product manuals.

Additional information on Industrial Security by Siemens can be found at: https://www.siemens.com/industrialsecurity

For more information about this issue, please see Siemens Security Advisory SSA-549234

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.

• Siemens