ICS Advisory (ICSA-20-224-05)

1. EXECUTIVE SUMMARY

• CVSS v3 3.1
• ATTENTION: Exploitable remotely/low skill level to exploit
• Vendor: Siemens
• Equipment: SIMATIC, SIMOTICS
• Vulnerability: TOCTOU Race Condition 

2. UPDATE INFORMATION

This updated advisory is a follow-up to the original advisory titled ICSA-20-224-05 Siemens SIMATIC, SIMOTICS that was published August 11, 2020, on the ICS webpage on us-cert.gov.

3. RISK EVALUATION

Successful exploitation of this vulnerability could allow an attacker to read a discrete set of traffic over the air after a Wi-Fi device state change.

4. TECHNICAL DETAILS

4.1 AFFECTED PRODUCTS

The following Siemens products are affected:

• SIMATIC RF350M: All versions
• SIMATIC RF650M: All versions

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• SIMOTICS CONNECT 400: All versions prior to 0.4.0.22

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4.2 VULNERABILITY OVERVIEW

4.2.1    TIME-OF-CHECK TIME-OF-USE (TOCTOU) RACE CONDITION) CWE-367

Specially timed and crafted traffic can cause internal errors (related to state transitions) in a WLAN device that can lead to improper Layer 2 Wi-Fi encryption and information disclosure over the air for a discrete set of traffic. This issue was discovered on Broadcom Wi-Fi client devices.

CVE-2019-15126 has been assigned to this vulnerability. A CVSS v3 base score of 3.1 has been calculated; the CVSS vector string is (AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N).

4.3 BACKGROUND

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

4.4 RESEARCHER

Siemens reported this vulnerability to CISA.

5. MITIGATIONS

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

• SIMATIC RF350M and RF650M: Disable Wi-Fi, if possible

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• SIMOTICS CONNECT 400: Update to v0.4.0.22

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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-712518

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.

No known public exploits specifically target this vulnerability.

This product is provided subject to this Notification and this Privacy & Use policy.