This updated advisory is a follow-up to the advisory update titled ICSA-20-042-05 Siemens SIMATIC S7 (Update A) that was published March 10, 2020, to the ICS webpage on us-cert.gov.
Successful exploitation of this vulnerability could allow remote attackers to perform a denial-of-service attack by sending a specially crafted HTTP request to the web server of an affected device.
The following versions of SIMATIC S7 devices are affected:
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Affected devices contain a vulnerability that could cause a denial-of-service condition of the web server by sending specially crafted HTTP requests to Ports 80/TCP and 443/TCP.
China Industrial Control Systems Cyber Emergency Response Team (CIC) reported this vulnerability to Siemens.
Siemens has identified the following specific workarounds and mitigations users can apply to reduce the risk:
For more information on this vulnerability and associated software updates, please see Siemens security advisory SSA-431678
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 this vulnerability.
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://www.us-cert.gov/ics
or incident reporting: https://www.us-cert.gov/report
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