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AUSCERT External Security Bulletin Redistribution
Advisory (icsa-21-040-07) Siemens SCALANCE W780 and W740
11 February 2021
AusCERT Security Bulletin Summary
Product: Siemens SCALANCE W780
Siemens SCALANCE W740
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2021-25666
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ICS Advisory (ICSA-21-040-07)
Siemens SCALANCE W780 and W740
Original release date: February 09, 2021
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1. EXECUTIVE SUMMARY
o CVSS v3 4.3
o ATTENTION: Exploitable remotely/low skill level to exploit
o Vendor: Siemens
o Equipment: SCALANCE W780 and W740
o Vulnerability: Allocation of Resources Without Limits or Throttling
2. RISK EVALUATION
Successful exploitation of this vulnerability could allow an attacker to cause
a denial-of-service condition.
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
The following Siemens products are affected:
o SCALANCE W780 and W740 (IEEE 802.11n) family: All versions prior to v6.3
3.2 VULNERABILITY OVERVIEW
3.2.1 ALLOCATION OF RESOURCES WITHOUT LIMITS OR THROTTLING CWE-770
Sending specially crafted packets through the ARP protocol to an affected
device could cause a partial denial-of-service condition, preventing the device
from operating normally for a short period.
CVE-2021-25666 has been assigned to this vulnerability. A CVSS v3 base score of
4.3 has been calculated; the CVSS vector string is ( AV:A/AC:L/PR:N/UI:N/S:U/
o CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing
o COUNTRIES/AREAS DEPLOYED: Worldwide
o COMPANY HEADQUARTERS LOCATION: Germany
Siemens ProductCERT reported this vulnerability to CISA.
Siemens recommends updating to the latest version:
o SCALANCE W780 and W740 (IEEE 802.11n) family: Update to v6.3 or later
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
CISA recommends users take defensive measures to minimize the risk of
exploitation of this vulnerability. Specifically, users should:
o Minimize network exposure for all control system devices and/or systems,
and ensure that they are not accessible from the Internet .
o Locate control system networks and remote devices behind firewalls, and
isolate them from the business network.
o When remote access is required, use secure methods, such as Virtual Private
Networks (VPNs), recognizing that VPNs may have vulnerabilities and should
be updated to the most current version available. Also recognize that VPN
is only as secure as the connected devices.
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
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
CISA continuously strives to improve its products and services. You can help by
choosing one of the links below to provide feedback about this product.
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