ICS Advisory (ICSA-20-042-10)

Siemens SCALANCE S-600 (Update A)

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1. EXECUTIVE SUMMARY

  • CVSS v3 7.5
  • ATTENTION: Exploitable remotely/Low skill level to exploit
  • Vendor: Siemens
  • Equipment: SCALANCE S-600 Firewall
  • Vulnerabilities: Resource Exhaustion, Cross-site Scripting

2. UPDATE INFORMATION

This updated advisory is a follow-up to the original advisory titled ICSA-20-042-10 Siemens SCALANCE S-600 that was published February 11, 2020 on the ICS webpage on us-cert.gov.

3. RISK EVALUATION

These vulnerabilities could allow a remote attacker to conduct denial-of-service or cross-site scripting attacks. User interaction is required for a successful exploitation of the cross-site-scripting attack.

4. TECHNICAL DETAILS

4.1 AFFECTED PRODUCTS

The following versions of SCALANCE S-600, are affected:

  • SCALANCE S602, all versions v3.0 or higher
  • SCALANCE S612, all versions v3.0 or higher
  • SCALANCE S623, all versions v3.0 or higher
  • SCALANCE S627-2M, all versions v3.0 or higher

4.2 VULNERABILITY OVERVIEW

4.2.1    CROSS-SITE SCRIPTING CWE-80

The integrated configuration web server of the affected devices could allow cross-site scripting (XSS) attacks if unsuspecting users are tricked into accessing a malicious link.

CVE-2019-6585 has been assigned to this vulnerability. A CVSS v3 base score of 4.7 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N).

4.2.2    UNCONTROLLED RESOURCE CONSUMPTION CWE-400

Specially crafted packets sent to Port 443/TCP of affected devices could cause a denial-of-service condition of the web server.

CVE-2019-13925 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).

4.2.3    UNCONTROLLED RESOURCE CONSUMPTION CWE-400

Specially crafted packets sent to Port 443/TCP of affected devices could cause a denial-of-service condition of the web server. A cold reboot is required to restore the functionality of the device.

CVE-2019-13926 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).

4.3 BACKGROUND

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

4.4 RESEARCHER

Melih Berk Ekşioğlu reported some of these vulnerabilities to Siemens.

5. MITIGATIONS

--------- Begin Update A Part 1 of 1 ---------

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

  • Only access links from trusted sources in the browser you use to access the SCALANCE S-600 administration website. 
  • For SCALANCE S-600 family (S602, S612, S623, S627-2M): migrate to a successor product within the SCALANCE SC-600 family, v2.1 or later version. For details refer to the notice of discontinuation.

--------- End Update A Part 1 of 1 ---------

For more information on these vulnerabilities and associated software updates, please see Siemens security advisory SSA-591405

CISA recommends users take defensive measures to minimize the risk of exploitation of these vulnerabilities. Specifically, users should take the following measures to protect themselves from social engineering attacks: 

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 these vulnerabilities.


Contact Information

For any questions related to this report, please contact the CISA at:

Email: CISAservicedesk@cisa.dhs.gov
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For industrial control systems cybersecurity information:  https://us-cert.cisa.gov/ics 
or incident reporting:  https://us-cert.cisa.gov/report

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