CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
PARTIAL
AV:N/AC:L/Au:N/C:N/I:N/A:P
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
AI Score
Confidence
High
EPSS
Percentile
59.8%
This updated advisory is a follow-up to the original advisory titled ICSA-21-257-16 Siemens SIPROTEC 5 that was published September 14, 2021, to the ICS webpage on us-cert.cisa.gov.
Successful exploitation of this vulnerability could allow unauthorized users to cause a denial-of-service condition by sending maliciously crafted web requests.
The following Siemens products are affected:
--------- Begin Update A Part 1 of 1 ---------
--------- End Update A Part 1 of 1 ---------
Received web packets are not properly processed. An unauthenticated remote attacker with access to any of the Ethernet interfaces could send specially crafted packets to force a restart of the target device.
CVE-2021-37206 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
Yuriy Strela from GAI NetConsult GmbH reported this vulnerability to Siemens.
Siemens recommends applying updates where available:
For remaining products, Siemens has identified the following specific workaround and mitigation users can apply to reduce the risk:
Operators of critical power systems (e.g., TSOs or DSOs) worldwide are usually required by regulations to build resilience into the power grids by applying multi-level redundant secondary protection schemes. Therefore, Siemens recommends operators check whether appropriate resilient protection measures are in place. The risk of cyber incidents impacting the gridβs reliability can thus be minimized by virtue of the grid design.
Siemens strongly recommends applying the provided security updates using the corresponding tooling and documented procedures made available with the product. If supported by the product, an automated means to apply the security updates across multiple product instances may be used. Siemens strongly recommends prior validation of any security update before being applied, and supervision by trained staff of the update process in the target environment.
As a general security measure Siemens strongly recommends protecting network access with appropriate mechanisms (e.g., firewalls, segmentation, VPN). It is advised users configure the environment according to Siemens operational guidelines for Digital Grid Products. in order to run the devices in a protected IT environment.
For additional information, please refer to Siemens Security Advisory SSA-500748
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.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-12-146-01BβTargeted 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.
web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-37206
cert-portal.siemens.com/productcert/pdf/ssa-500748.pdf
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cwe.mitre.org/data/definitions/20.html
public.govdelivery.com/accounts/USDHSCISA/subscriber/new?topic_id=USDHSCISA_138
support.industry.siemens.com/cs/ww/en/view/109740816
support.industry.siemens.com/cs/ww/en/view/109740816
support.industry.siemens.com/cs/ww/en/view/109740816
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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
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CVSS2
Attack Vector
NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
PARTIAL
AV:N/AC:L/Au:N/C:N/I:N/A:P
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
AI Score
Confidence
High
EPSS
Percentile
59.8%