1. EXECUTIVE SUMMARY
- CVSS v3 6.8
- ATTENTION: Low skill level to exploit
- Vendor: Siemens
- Equipment: S7-1200 CPU family (including SIPLUS variants); S7-200 SMART CPU family
- Vulnerability: Exposed Dangerous Method or Function
2. UPDATE INFORMATION
This updated advisory is a follow-up to the advisory update titled-19-318-02 Siemens S7-1200 (Update A) that was published December 10, 2019, on the ICS webpage on us-cert.gov.
3. RISK EVALUATION
Successful exploitation of this vulnerability could expose additional diagnostic functionality to an attacker with physical access to the UART interface during boot process.
4. TECHNICAL DETAILS
4.1 AFFECTED PRODUCTS
The following Siemens products are affected:
——— Begin Update B Part 1 of 2 ———
- SIMATIC S7-1200 CPU family v4.x (including SIPLUS variants): all versions with Function State (FS) < 11;
- SIMATIC S7-1200 CPU family prior to v4.x (including SIPLUS variants): all versions.
- SIMATIC S7-200 SMART CPU ST20 (6ES7 288-1ST20-0AA0): all versions prior to and including v2.5.0 and Function State (FS) <= 9.
- SIMATIC S7-200 SMART CPU ST30 (6ES7 288-1ST30-0AA0): all versions prior to and including v2.5.0 and Function State (FS) <= 9.
- SIMATIC S7-200 SMART CPU ST40 (6ES7 288-1ST40-0AA0): all versions prior to and including v2.5.0 and Function State (FS) <= 8.
- SIMATIC S7-200 SMART CPU ST60 (6ES7 288-1ST60-0AA0): all versions prior to and including v2.5.0 and Function State (FS) <= 8.
- SIMATIC S7-200 SMART CPU SR20 (6ES7 288-1SR20-0AA0): all versions prior to and including v2.5.0 and Function State (FS) <= 11.
- SIMATIC S7-200 SMART CPU SR30 (6ES7 288-1SR30-0AA0): all versions prior to and including v2.5.0 and Function State (FS) <= 10.
- SIMATIC S7-200 SMART CPU SR40 (6ES7 288-1SR40-0AA0): all versions prior to and including v2.5.0 and Function State (FS) <= 10.
- SIMATIC S7-200 SMART CPU SR60 (6ES7 288-1SR60-0AA0): all versions prior to and including v2.5.0 and Function State (FS) <= 12.
- SIMATIC S7-200 SMART CPU CR40 (6ES7 288-1CR40-0AA0): all versions prior to and including v2.2.2 and Function State (FS) <= 8.
- SIMATIC S7-200 SMART CPU CR60 (6ES7 288-1CR60-0AA0): all versions prior to and including v2.2.2 and Function State (FS) <= 10.
- SIMATIC S7-200 SMART CPU CR20s (6ES7 288-1CR20-0AA0): all versions prior to and including v2.3.0 and Function State (FS) <= 3.
- SIMATIC S7-200 SMART CPU CR30s (6ES7 288-1CR30-0AA0): all versions prior to and including v2.3.0 and Function State (FS) <= 3.
- SIMATIC S7-200 SMART CPU CR40s (6ES7 288-1CR40-0AA0): all versions prior to and including v2.3.0 and Function State (FS) <= 3.
- SIMATIC S7-200 SMART CPU CR60s (6ES7 288-1CR60-0AA0): all versions prior to and including v2.3.0 and Function State (FS) <= 3.
——— End Update B Part 1 of 2 ———
4.2 VULNERABILITY OVERVIEW
4.2.1 EXPOSED DANGEROUS METHOD OR FUNCTION CWE-749
An attacker with physical access to the UART interface could access additional diagnostic functionality. Successful exploitation could compromise confidentiality, integrity, and availability of the affected system.
CVE-2019-13945 has been assigned to this vulnerability. A CVSS v3 base score of 6.8 has been calculated; the CVSS vector string is
(AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).
4.3 BACKGROUND
- CRITICAL INFRASTRUCTURE SECTORS: Chemical, Critical Manufacturing, Energy, Food and Agriculture, Water and Wastewater Systems
- COUNTRIES/AREAS DEPLOYED: Worldwide
- COMPANY HEADQUARTERS LOCATION: Germany
4.4 RESEARCHER
Ali Abbasi from Ruhr University of Bochum reported this vulnerability to Siemens.
5. MITIGATIONS
Siemens has identified the following specific mitigations for the referenced products:
——— Begin Update B Part 2 of 2 ———
- SIMATIC S7-1200 CPU family v4.x (including SIPLUS variants): Update to v4.4.1 and (FS) >= 11.
- SIMATIC S7-1200 CPU family prior to v4.x (including SIPLUS variants): Firmware versions prior to v4.x cannot be updated; for remediation see the workaround recommendations below.
- SIMATIC S7-200 SMART CPU ST20 (6ES7 288-1ST20-0AA0): Update to version >= v2.5.1 and the latest boot loader version.
- SIMATIC S7-200 SMART CPU ST30 (6ES7 288-1ST30-0AA0): Update to version >= v2.5.1 and the latest boot loader version.
- SIMATIC S7-200 SMART CPU ST40 (6ES7 288-1ST40-0AA0): Update to version >= v2.5.1 and the latest boot loader version.
- SIMATIC S7-200 SMART CPU ST60 (6ES7 288-1ST60-0AA0): Update to version >= v2.5.1 and the latest boot loader version.
- SIMATIC S7-200 SMART CPU SR20 (6ES7 288-1SR20-0AA0): Update to version >= v2.5.1 and the latest boot loader version.
- SIMATIC S7-200 SMART CPU SR30 (6ES7 288-1SR30-0AA0): Update to version >= v2.5.1 and the latest boot loader version.
- SIMATIC S7-200 SMART CPU SR40 (6ES7 288-1SR40-0AA0): Update to version >= v2.5.1 and the latest boot loader version.
- SIMATIC S7-200 SMART CPU SR60 (6ES7 288-1SR60-0AA0): Update to version >= v2.5.1 and the latest boot loader version.
- SIMATIC S7-200 SMART CPU CR40 (6ES7 288-1CR40-0AA0): Update to version >= v2.2.3 and the latest boot loader version.
- SIMATIC S7-200 SMART CPU CR60 (6ES7 288-1CR60-0AA0): Update to version >= v2.2.3 and the latest boot loader version.
- SIMATIC S7-200 SMART CPU CR20s (6ES7 288-1CR20-0AA0): Update to version >= v2.3.0 and the latest boot loader version (the firmware version currently remains at v2.3.0; only the boot loader updates).
- SIMATIC S7-200 SMART CPU CR30s (6ES7 288-1CR30-0AA0): Update to version >= v2.3.0 and the latest boot loader version (the firmware version currently remains at v2.3.0; only the boot loader updates).
- SIMATIC S7-200 SMART CPU CR40s (6ES7 288-1CR40-0AA0): Update to version >= v2.3.0 and the latest boot loader version (the firmware version currently remains at v2.3.0; only the boot loader updates).
- SIMATIC S7-200 SMART CPU CR60s (6ES7 288-1CR60-0AA0): Update to version >= v2.3.0 and the latest boot loader version (the firmware version currently remains at v2.3.0; only the boot loader updates).
——— End Update B Part 2 of 2 ———
Siemens has identified the following specific workarounds and mitigations users can apply to reduce the risk:
- Ensure physical access protection.
- Apply Defense-in-Depth.
As a general security measure, Siemens strongly recommends protecting network access to devices with appropriate mechanisms. Siemens recommends users configure their environment according to the Siemens Operational Guidelines for Industrial Security and follow the recommendations in the product manuals to operate the devices in a protected environment.
Additional information on industrial security by Siemens can be found at: https://www.siemens.com/industrialsecurity.
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.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.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.
This vulnerability is not exploitable remotely; no known public exploits specifically target this vulnerability.
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