CVSS2
Attack Vector
NETWORK
Attack Complexity
MEDIUM
Authentication
NONE
Confidentiality Impact
PARTIAL
Integrity Impact
NONE
Availability Impact
NONE
AV:N/AC:M/Au:N/C:P/I:N/A:N
CVSS3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
NONE
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
AI Score
Confidence
High
EPSS
Percentile
41.2%
This updated advisory is a follow-up to the advisory update titled ICSA-21-012-02 Siemens SCALANCE X Switches (Update B) that was published February 14, 2021, to the ICS webpage on us-cert.cisa.gov.
Successful exploitation of these vulnerabilities could allow an attacker to execute a man-in-the-middle attack and decrypt previously captured traffic.
The following Siemens products are affected:
--------- Begin Update C Part 1 of 2 ---------
--------- End Update C Part 1 of 2 ---------
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 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N).
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).
Siemens ProductCERT reported these vulnerabilities to CISA.
Siemens recommends applying updates where available:
--------- Begin Update C Part 2 of 2 ---------
--------- End Update C Part 2 of 2 ---------
Siemens has identified the following specific workarounds and mitigations users can apply to reduce the risk:
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 these vulnerabilities. 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.
web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2020-28391
web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2020-28395
cert-portal.siemens.com/operational-guidelines-industrial-security.pdf
cert-portal.siemens.com/productcert/pdf/ssa-274900.pdf
cisasurvey.gov1.qualtrics.com/jfe/form/SV_9n4TtB8uttUPaM6?product=https://www.cisa.gov/news-events/ics-advisories/icsa-21-012-02
cwe.mitre.org/data/definitions/321.html
cwe.mitre.org/data/definitions/321.html
public.govdelivery.com/accounts/USDHSCISA/subscriber/new?topic_id=USDHSCISA_138
support.industry.siemens.com/cs/ww/en/view/109773547/
support.industry.siemens.com/cs/ww/en/view/109792534/
support.industry.siemens.com/cs/ww/en/view/109801131/
support.industry.siemens.com/cs/ww/en/view/109814809/
twitter.com/CISAgov
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us-cert.cisa.gov/ics
us-cert.cisa.gov/ics/recommended-practices
us-cert.cisa.gov/ics/tips/ICS-TIP-12-146-01B
us-cert.cisa.gov/sites/default/files/recommended_practices/NCCIC_ICS-CERT_Defense_in_Depth_2016_S508C.pdf
www.dhs.gov
www.dhs.gov/foia
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www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
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CVSS2
Attack Vector
NETWORK
Attack Complexity
MEDIUM
Authentication
NONE
Confidentiality Impact
PARTIAL
Integrity Impact
NONE
Availability Impact
NONE
AV:N/AC:M/Au:N/C:P/I:N/A:N
CVSS3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
NONE
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
AI Score
Confidence
High
EPSS
Percentile
41.2%