Siemens SIMATIC S7-200 SMART Devices

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). 

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1. EXECUTIVE SUMMARY

• CVSS v4 8.8
• ATTENTION: Exploitable remotely/low attack complexity
• Vendor: Siemens
• Equipment: SIMATIC S7-200 SMART devices
• Vulnerability: Use of Insufficiently Random Values

2. RISK EVALUATION

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

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following Siemens programmable logic controllers are affected:

• Siemens SIMATIC S7-200 SMART CPU CR40 (6ES7288-1CR40-0AA0): All versions
• Siemens SIMATIC S7-200 SMART CPU CR60 (6ES7288-1CR60-0AA0): All versions
• Siemens SIMATIC S7-200 SMART CPU SR20 (6ES7288-1SR20-0AA0): All versions
• Siemens SIMATIC S7-200 SMART CPU SR20 (6ES7288-1SR20-0AA1): All versions
• Siemens SIMATIC S7-200 SMART CPU SR30 (6ES7288-1SR30-0AA0): All versions
• Siemens SIMATIC S7-200 SMART CPU SR30 (6ES7288-1SR30-0AA1): All versions
• Siemens SIMATIC S7-200 SMART CPU SR40 (6ES7288-1SR40-0AA0): All versions
• Siemens SIMATIC S7-200 SMART CPU SR40 (6ES7288-1SR40-0AA1): All versions
• Siemens SIMATIC S7-200 SMART CPU SR60 (6ES7288-1SR60-0AA0): All versions
• Siemens SIMATIC S7-200 SMART CPU SR60 (6ES7288-1SR60-0AA1): All versions
• Siemens SIMATIC S7-200 SMART CPU ST20 (6ES7288-1ST20-0AA0): All versions
• Siemens SIMATIC S7-200 SMART CPU ST20 (6ES7288-1ST20-0AA1): All versions
• Siemens SIMATIC S7-200 SMART CPU ST30 (6ES7288-1ST30-0AA0): All versions
• Siemens SIMATIC S7-200 SMART CPU ST30 (6ES7288-1ST30-0AA1): All versions
• Siemens SIMATIC S7-200 SMART CPU ST40 (6ES7288-1ST40-0AA0): All versions
• Siemens SIMATIC S7-200 SMART CPU ST40 (6ES7288-1ST40-0AA1): All versions
• Siemens SIMATIC S7-200 SMART CPU ST60 (6ES7288-1ST60-0AA0): All versions
• Siemens SIMATIC S7-200 SMART CPU ST60 (6ES7288-1ST60-0AA1): All versions

3.2 Vulnerability Overview

3.2.1 USE OF INSUFFICIENTLY RANDOM VALUES CWE-330

Affected devices are using a predictable IP ID sequence number. This leaves the system susceptible to a family of attacks which rely on the use of predictable IP ID sequence numbers as their base method of attack and eventually could allow an attacker to create a denial-of-service condition.

CVE-2024-35292 has been assigned to this vulnerability. A CVSS v3 base score of 8.2 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H).

A CVSS v4 score has also been calculated for CVE-2024-35292. A base score of 8.8 has been calculated; the CVSS vector string is (CVSS4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N).

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

• Restrict access to the network where the affected products are located by introducing strict access control mechanisms.

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-481506 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

• June 13, 2024: Initial Publication

• Siemens