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AUSCERT External Security Bulletin Redistribution
ESB-2021.0124
Advisory (icsa-21-012-02) Siemens SCALANCE X Switches
13 January 2021
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AusCERT Security Bulletin Summary
---------------------------------
Product: Siemens SCALANCE X Switches
Publisher: ICS-CERT
Operating System: Network Appliance
Impact/Access: Access Confidential Data -- Remote/Unauthenticated
Reduced Security -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2020-28395 CVE-2020-28391
Original Bulletin:
https://us-cert.cisa.gov/ics/advisories/icsa-21-012-02
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ICS Advisory (ICSA-21-012-02)
Siemens SCALANCE X Switches
Original release date: January 12, 2021
Legal Notice
All information products included in https://us-cert.cisa.gov/ics are provided
"as is" for informational purposes only. The Department of Homeland Security
(DHS) does not provide any warranties of any kind regarding any information
contained within. DHS does not endorse any commercial product or service,
referenced in this product or otherwise. Further dissemination of this product
is governed by the Traffic Light Protocol (TLP) marking in the header. For more
information about TLP, see https://us-cert.cisa.gov/tlp/ .
1. EXECUTIVE SUMMARY
o CVSS v3 9.1
o ATTENTION: Exploitable remotely/low skill level to exploit
o Vendor: Siemens
o Equipment: SCALANCE X200, X200IRT, X300
o Vulnerabilities: Use of Hard-coded Cryptographic Key
2. RISK EVALUATION
Successful exploitation of these vulnerabilities could allow an attacker to
execute a man-in-the-middle attack and decrypt previously captured traffic.
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
The following Siemens products are affected:
o SCALANCE X-200 switch family (incl. SIPLUS NET variants): All versions
o SCALANCE X-200IRT switch family (incl. SIPLUS NET variants): All versions
o SCALANCE X-300 switch family (incl. X408 and SIPLUS NET variants): All
versions prior to v4.1.0
3.2 VULNERABILITY OVERVIEW
3.2.1 USE OF HARD-CODED CRYPTOGRAPHIC KEY CWE-321
Devices create a new unique key upon factory reset, except when used with
C-PLUG. When used with C-PLUG the devices use the hardcoded private RSA-key
shipped with the firmware-image. An attacker could exploit this vulnerability
to create a man-in-the-middle situation and decrypt previously captured
traffic.
CVE-2020-28391 has been assigned to this vulnerability. A CVSS v3 base score of
9.1 has been calculated; the CVSS vector string is (A AV:N/AC:L/PR:N/UI:N/S:U/
C:H/I:H/A:N ).
3.2.2 USE OF HARD-CODED CRYPTOGRAPHIC KEY CWE-321
Devices do not create a new unique private key after factory reset. An attacker
could exploit this vulnerability to create a man-in-the-middle situation and
decrypt previously captured traffic.
CVE-2020-28395 has been assigned to this vulnerability. A CVSS v3 base score of
9.1 has been calculated; the CVSS vector string is ( AV:N/AC:L/PR:N/UI:N/S:U/
C:H/I:H/A:N ).
3.3 BACKGROUND
o CRITICAL INFRASTRUCTURE SECTORS: Multiple Sectors
o COUNTRIES/AREAS DEPLOYED: Worldwide
o COMPANY HEADQUARTERS LOCATION: Germany
3.4 RESEARCHER
Siemens ProductCERT reported these vulnerabilities to CISA.
4. MITIGATIONS
Siemens recommends applying updates where available:
o SCALANCE X-300 switch family (incl. X408 and SIPLUS NET variants): Update
to v4.1.0 or later
Siemens has identified the following specific workarounds and mitigations users
can apply to reduce the risk:
o Update the default self-signed device X.509 certificates with own trusted
certificate.
o Update the default hardcoded X.509 certificates from the firmware image
(fingerprints SHA-1:
F2:C8:3B:8F:86:27:74:AA:60:EC:D4:A0:CF:0D:BE:A6:D1:FE:22:12 and SHA-256:
25:60:DB:B3:
F9:07:9D:69:0E:DD:A9:EB:4E:1C:D5:8E:AF:79:16:C3:C8:13:A6:F6:59:AD:05:E4:6F:77:F7:72)
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
SSA-274900
CISA recommends users take defensive measures to minimize the risk of
exploitation of this vulnerability. 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.
For any questions related to this report, please contact the CISA at:
Email: CISAservicedesk@cisa.dhs.gov
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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