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This updated advisory is a follow-up to the updated advisory titled ICSA-17-332-01 Siemens SCALANCE W1750D, M800, and S615 (Update B) that was published May 10, 2018, to the ICS webpage on us-cert.gov.
Successful exploitation of these vulnerabilities could allow a remote attacker to crash the DNS service or execute arbitrary code by crafting malicious DNS responses.
The following versions of SCALANCE, network interfaces, are affected:
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An attacker can cause a crash of the DNSmasq process by sending specially crafted request messages to the service.
The following CVEs have been assigned to this group of vulnerabilities: CVE-2017-13704, CVE-2017-14495, CVE-2017-14496
A CVSS v3 base score of 5.3 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).
An attacker can cause a crash or execute arbitrary code by sending specially crafted DNS responses to the DNSmasq process. In order to exploit this vulnerability, an attacker must be able to trigger DNS requests from the device and must be in a position that allows the injection of malicious DNS responses.
Siemens Product CERT reported these vulnerabilities to CISA.
Siemens reports they are preparing updates for the affected products and recommends the following mitigations until patches are available:
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Siemens has produced advisory SSA-689071 to address these vulnerabilities.
CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability. Specifically, users should:
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.
For any questions related to this report, please contact the CISA at:
Toll Free: 1-888-282-0870
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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