CVSS2
Attack Vector
NETWORK
Attack Complexity
MEDIUM
Authentication
NONE
Confidentiality Impact
PARTIAL
Integrity Impact
NONE
Availability Impact
PARTIAL
AV:N/AC:M/Au:N/C:P/I:N/A:P
CVSS3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H
AI Score
Confidence
High
EPSS
Percentile
73.9%
This updated advisory is a follow-up to the original advisory titled ICSA-21-103-13 Siemens SIMOTICS CONNECT 400 that was published April 13, 2021, on the ICS webpage on www.cisa.gov/uscert.
Successful exploitation of these vulnerabilities could allow an attacker to poison the DNS cache or spoof DNS resolving.
The following products and versions are affected:
β’ SIMOTICS CONNECT 400, All versions prior to v0.5.0.0
β’ SIMOTICS CONNECT 400, v0.5.0.0 and later only affected by CVE-2021-25677
The DNS domain name label parsing functionality does not properly validate the null-terminated name in DNS-responses. The parsing of malformed responses could result in a read past the end of an allocated structure. An attacker with a privileged position in the network could leverage this vulnerability to cause a denial-of-service condition or leak the read memory.
CVE-2020-27736 has been assigned to this vulnerability. A CVSS v3 base score of 6.5 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H).
The DNS response parsing functionality does not properly validate various length and counts of the records. The parsing of malformed responses could result in a read past the end of an allocated structure. An attacker with a privileged position in the network could leverage this vulnerability to cause a denial-of-service condition or leak the memory past the allocated structure.
CVE-2020-27737 has been assigned to this vulnerability. A CVSS v3 base score of 6.5 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H).
The DNS domain name record decompression functionality does not properly validate the pointer offset values. The parsing of malformed responses could result in a read access past the end of an allocated structure. An attacker with a privileged position in the network could leverage this vulnerability to cause a denial-of-service condition.
CVE-2020-27738 has been assigned to this vulnerability. A CVSS v3 base score of 6.5 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H).
The DNS client does not properly randomize DNS transaction IDs. This could allow an attacker to poison the DNS cache or spoof DNS resolving.
CVE-2021-25677 has been assigned to this vulnerability. A CVSS v3 base score of 5.3 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N).
Siemens reported these vulnerabilities to CISA.
Siemens has identified the following specific workarounds and mitigations users can apply to reduce risk:
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For additional information, please refer to Siemens Security Advisory SSA-669158
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 Siemens operational guidelines for Industrial Security, and following the recommendations in the product manuals.
For further inquiries on security vulnerabilities in Siemensβ products and solutions, please contact Siemens ProductCERT.
CISA recommends users take defensive measures to minimize the risk of exploitation of these vulnerabilities. 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 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 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 these vulnerabilities.
web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2020-27736
web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2020-27737
web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2020-27738
web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-25677
web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-25677
cert-portal.siemens.com/productcert/pdf/ssa-669158.pdf
cert-portal.siemens.com/productcert/pdf/ssa-669158.pdf
cisasurvey.gov1.qualtrics.com/jfe/form/SV_9n4TtB8uttUPaM6?product=https://www.cisa.gov/news-events/ics-advisories/icsa-21-103-13
cwe.mitre.org/data/definitions/125.html
cwe.mitre.org/data/definitions/170.html
cwe.mitre.org/data/definitions/788.html
cwe.mitre.org/data/definitions/788.html
public.govdelivery.com/accounts/USDHSCISA/subscriber/new?topic_id=USDHSCISA_138
support.industry.siemens.com/cs/ww/en/view/109778383/
support.industry.siemens.com/cs/ww/en/view/109778383/
twitter.com/CISAgov
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www.cisa.gov/uscert/ics
www.cisa.gov/uscert/ics
www.cisa.gov/uscert/ics/alerts/ICS-ALERT-10-301-01
www.cisa.gov/uscert/ics/recommended-practices
www.cisa.gov/uscert/ics/tips/ICS-TIP-12-146-01B
www.cisa.gov/uscert/sites/default/files/recommended_practices/NCCIC_ICS-CERT_Defense_in_Depth_2016_S508C.pdf
www.dhs.gov
www.dhs.gov/foia
www.dhs.gov/performance-financial-reports
www.facebook.com/CISA
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www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H
www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H
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www.oig.dhs.gov/
www.siemens.com/cert/advisories
www.siemens.com/cert/operational-guidelines-industrial-security
www.usa.gov/
www.whitehouse.gov/
www.youtube.com/@cisagov
mailto:?subject=Siemens%20SIMOTICS%20CONNECT%20400%20%28Update%20A%29&body=www.cisa.gov/news-events/ics-advisories/icsa-21-103-13
CVSS2
Attack Vector
NETWORK
Attack Complexity
MEDIUM
Authentication
NONE
Confidentiality Impact
PARTIAL
Integrity Impact
NONE
Availability Impact
PARTIAL
AV:N/AC:M/Au:N/C:P/I:N/A:P
CVSS3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H
AI Score
Confidence
High
EPSS
Percentile
73.9%