{
  "document": {
    "acknowledgments": [
      {
        "organization": "Siemens ProductCERT",
        "summary": "reporting this vulnerability to CISA."
      },
      {
        "names": [
          "Daniel dos Santos"
        ],
        "organization": "Forescout Technologies Inc.",
        "summary": "coordinated disclosure"
      }
    ],
    "category": "csaf_security_advisory",
    "csaf_version": "2.0",
    "distribution": {
      "text": "Disclosure is not limited",
      "tlp": {
        "label": "WHITE",
        "url": "https://us-cert.cisa.gov/tlp/"
      }
    },
    "notes": [
      {
        "category": "summary",
        "text": "Security researchers discovered and disclosed 9 vulnerabilities in several DNS implementations, also known as \u201cNAME:WRECK\u201d vulnerabilities. The vulnerability described in this advisory is from this set.\n\nThe DNS client of of the networking component (Nucleus NET) in Nucleus Real-Time Operating System (RTOS) contains a vulnerability related to the handling of UDP port numbers in DNS requests that could allow an attacker to poison the DNS cache or spoof DNS resolving.\n\nSiemens has released updates for several affected products and recommends to update to the latest versions. Siemens recommends specific countermeasures for products where updates are not available.",
        "title": "Summary"
      },
      {
        "category": "general",
        "text": "As a general security measure, Siemens strongly recommends to protect network access to devices with appropriate mechanisms. In order to operate the devices in a protected IT environment, Siemens recommends to configure the environment according to Siemens\u0027 operational guidelines for Industrial Security (Download: https://www.siemens.com/cert/operational-guidelines-industrial-security), and to follow the recommendations in the product manuals.\n\nAdditional information on Industrial Security by Siemens can be found at: https://www.siemens.com/industrialsecurity",
        "title": "General Recommendations"
      },
      {
        "category": "general",
        "text": "For further inquiries on security vulnerabilities in Siemens products and solutions, please contact the Siemens ProductCERT: https://www.siemens.com/cert/advisories",
        "title": "Additional Resources"
      },
      {
        "category": "legal_disclaimer",
        "text": "Siemens Security Advisories are subject to the terms and conditions contained in Siemens\u0027 underlying license terms or other applicable agreements previously agreed to with Siemens (hereinafter \"License Terms\"). To the extent applicable to information, software or documentation made available in or through a Siemens Security Advisory, the Terms of Use of Siemens\u0027 Global Website (https://www.siemens.com/terms_of_use, hereinafter \"Terms of Use\"), in particular Sections 8-10 of the Terms of Use, shall apply additionally. In case of conflicts, the License Terms shall prevail over the Terms of Use.",
        "title": "Terms of Use"
      },
      {
        "category": "legal_disclaimer",
        "text": "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/.",
        "title": "Legal Notice"
      },
      {
        "category": "other",
        "text": "This CISA CSAF advisory was converted from Siemens ProductCERT\u0027s CSAF advisory.",
        "title": "Advisory Conversion Disclaimer"
      },
      {
        "category": "other",
        "text": "Multiple",
        "title": "Critical infrastructure sectors"
      },
      {
        "category": "other",
        "text": "Worldwide",
        "title": "Countries/areas deployed"
      },
      {
        "category": "other",
        "text": "Germany",
        "title": "Company headquarters location"
      },
      {
        "category": "general",
        "text": "CISA recommends users take defensive measures to minimize the exploitation risk of these vulnerabilities.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "Minimize network exposure for all control system devices and/or systems, and ensure they are not accessible from the internet.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "Locate control system networks and remote devices behind firewalls and isolate them from business networks.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "When remote access is required, use more secure methods, such as Virtual Private Networks (VPNs), recognizing VPNs may have vulnerabilities and should be updated to the most recent version available. Also recognize VPN is only as secure as its connected devices.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "CISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "CISA also provides a section for control systems security recommended practices on the ICS webpage on cisa.gov. Several CISA products detailing cyber defense best practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "CISA encourages organizations to implement recommended cybersecurity strategies for proactive defense of ICS assets. Additional mitigation guidance and recommended practices are publicly available on the ICS webpage at cisa.gov in the technical information paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies.",
        "title": "Recommended Practices"
      },
      {
        "category": "general",
        "text": "Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents.",
        "title": "Recommended Practices"
      }
    ],
    "publisher": {
      "category": "other",
      "contact_details": "central@cisa.dhs.gov",
      "name": "CISA",
      "namespace": "https://www.cisa.gov/"
    },
    "references": [
      {
        "category": "self",
        "summary": "SSA-201384: Predictable UDP Port Number Vulnerability (NAME:WRECK) in the DNS Module of Nucleus RTOS - CSAF Version",
        "url": "https://cert-portal.siemens.com/productcert/csaf/ssa-201384.json"
      },
      {
        "category": "self",
        "summary": "SSA-201384: Predictable UDP Port Number Vulnerability (NAME:WRECK) in the DNS Module of Nucleus RTOS - TXT Version",
        "url": "https://cert-portal.siemens.com/productcert/txt/ssa-201384.txt"
      },
      {
        "category": "self",
        "summary": "SSA-201384: Predictable UDP Port Number Vulnerability (NAME:WRECK) in the DNS Module of Nucleus RTOS - PDF Version",
        "url": "https://cert-portal.siemens.com/productcert/pdf/ssa-201384.pdf"
      },
      {
        "category": "self",
        "summary": "ICS Advisory ICSA-21-103-14 JSON",
        "url": "https://raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/OT/white/2021/icsa-21-103-14.json"
      },
      {
        "category": "self",
        "summary": "ICS Advisory ICSA-21-103-14 - Web Version",
        "url": "https://www.cisa.gov/news-events/ics-advisories/icsa-21-103-14"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/uscert/ics/alerts/ICS-ALERT-10-301-01"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/resources-tools/resources/ics-recommended-practices"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/topics/industrial-control-systems"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://us-cert.cisa.gov/sites/default/files/recommended_practices/NCCIC_ICS-CERT_Defense_in_Depth_2016_S508C.pdf"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/sites/default/files/publications/Cybersecurity_Best_Practices_for_Industrial_Control_Systems.pdf"
      },
      {
        "category": "external",
        "summary": "Recommended Practices",
        "url": "https://www.cisa.gov/uscert/ics/tips/ICS-TIP-12-146-01B"
      }
    ],
    "title": "Siemens Nucleus DNS (Update A)",
    "tracking": {
      "current_release_date": "2025-05-06T06:00:00.000000Z",
      "generator": {
        "engine": {
          "name": "CISA CSAF Generator",
          "version": "1.0.0"
        }
      },
      "id": "ICSA-21-103-14",
      "initial_release_date": "2021-04-13T00:00:00.000000Z",
      "revision_history": [
        {
          "date": "2021-04-13T00:00:00.000000Z",
          "legacy_version": "1.0",
          "number": "1",
          "summary": "Publication Date"
        },
        {
          "date": "2021-11-09T00:00:00.000000Z",
          "legacy_version": "1.1",
          "number": "2",
          "summary": "Consolidated list of products"
        },
        {
          "date": "2022-01-11T00:00:00.000000Z",
          "legacy_version": "1.2",
          "number": "3",
          "summary": "Removed CAPITAL VSTAR as not affected"
        },
        {
          "date": "2025-05-06T06:00:00.000000Z",
          "legacy_version": "Revision",
          "number": "4",
          "summary": "Revision - Fixing typos"
        }
      ],
      "status": "final",
      "version": "4"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "vers:all/*",
                "product": {
                  "name": "Nucleus NET",
                  "product_id": "CSAFPID-0001"
                }
              }
            ],
            "category": "product_name",
            "name": "Nucleus NET"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "\u003cV2013.08",
                "product": {
                  "name": "Nucleus ReadyStart V3",
                  "product_id": "CSAFPID-0002"
                }
              }
            ],
            "category": "product_name",
            "name": "Nucleus ReadyStart V3"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "including_affected_DNS_modules",
                "product": {
                  "name": "Nucleus Source Code",
                  "product_id": "CSAFPID-0003"
                }
              }
            ],
            "category": "product_name",
            "name": "Nucleus Source Code"
          }
        ],
        "category": "vendor",
        "name": "Siemens"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2021-27393",
      "cwe": {
        "id": "CWE-330",
        "name": "Use of Insufficiently Random Values"
      },
      "notes": [
        {
          "category": "summary",
          "text": "The DNS client does not properly randomize UDP port numbers of DNS requests. That could allow an attacker to poison the DNS cache or spoof DNS resolving.",
          "title": "Summary"
        }
      ],
      "product_status": {
        "known_affected": [
          "CSAFPID-0001",
          "CSAFPID-0002",
          "CSAFPID-0003"
        ]
      },
      "references": [
        {
          "summary": "CVE-2021-27393 - Nucleus ReadyStart V3",
          "url": "https://support.sw.siemens.com/en-US/product/1009925838/"
        },
        {
          "summary": "CVE-2021-27393 Mitre 5.0 json",
          "url": "https://cert-portal.siemens.com/productcert/mitre/CVE-2021-27393.json"
        }
      ],
      "remediations": [
        {
          "category": "mitigation",
          "details": "Update to the latest version of Nucleus ReadyStart V3 or V4",
          "product_ids": [
            "CSAFPID-0001"
          ]
        },
        {
          "category": "mitigation",
          "details": "Contact customer support or your local Nucleus Sales team for mitigation advice",
          "product_ids": [
            "CSAFPID-0001"
          ]
        },
        {
          "category": "no_fix_planned",
          "details": "Currently no remediation is planned",
          "product_ids": [
            "CSAFPID-0001"
          ]
        },
        {
          "category": "vendor_fix",
          "details": "Update to V2013.08 or later version",
          "product_ids": [
            "CSAFPID-0002"
          ],
          "url": "https://support.sw.siemens.com/en-US/product/1009925838/"
        },
        {
          "category": "vendor_fix",
          "details": "Contact customer support to receive patch and update information",
          "product_ids": [
            "CSAFPID-0003"
          ]
        },
        {
          "category": "mitigation",
          "details": "Avoid using DNS client of affected versions",
          "product_ids": [
            "CSAFPID-0001",
            "CSAFPID-0002",
            "CSAFPID-0003"
          ]
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C",
            "version": "3.1"
          },
          "products": [
            "CSAFPID-0001",
            "CSAFPID-0002",
            "CSAFPID-0003"
          ]
        }
      ],
      "title": "CVE-2021-27393"
    }
  ]
}