1. EXECUTIVE SUMMARY
- CVSS v3 7.5
- ATTENTION: Exploitable remotely/low attack complexity
- 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 advisory update titled ICSA-20-042-10 Siemens SCALANCE S-600 (Update A) that was published August 11, 2020 to the ICS webpage on us-cert.cisa.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:
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- SCALANCE S602, all versions v3.0 or higher and prior to v4.1
- SCALANCE S612, all versions v3.0 or higher and prior to v4.1
- SCALANCE S623, all versions v3.0 or higher and prior to v4.1
- SCALANCE S627-2M, all versions v3.0 or higher and prior to v4.1
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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
Siemens has identified the following specific workarounds and mitigations that customers can apply to reduce the risk:
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- For versions v3.0 and higher, Update to v4.1
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- 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.
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:
- Do not click web links or open unsolicited attachments in email messages.
- Refer to Recognizing and Avoiding Email Scams for more information on avoiding email scams.
- Refer to Avoiding Social Engineering and Phishing Attacks for more information on 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.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 these vulnerabilities.
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