{"api_version":"1","generated_at":"2026-07-23T14:55:48+00:00","cve":"CVE-2020-27213","urls":{"html":"https://cve.report/CVE-2020-27213","api":"https://cve.report/api/cve/CVE-2020-27213.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2020-27213","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2020-27213"},"summary":{"title":"CVE-2020-27213","description":"An issue was discovered in Ethernut Nut/OS 5.1. The code that generates Initial Sequence Numbers (ISNs) for TCP connections derives the ISN from an insufficiently random source. As a result, an attacker may be able to determine the ISN of current and future TCP connections and either hijack existing ones or spoof future ones. While the ISN generator seems to adhere to RFC 793 (where a global 32-bit counter is incremented roughly every 4 microseconds), proper ISN generation should aim to follow at least the specifications outlined in RFC 6528.","state":"PUBLIC","assigner":"cve@mitre.org","published_at":"2023-10-10 17:15:00","updated_at":"2023-10-27 19:34:00"},"problem_types":["CWE-330"],"metrics":[],"references":[{"url":"http://www.ethernut.de/en/download/index.html","name":"http://www.ethernut.de/en/download/index.html","refsource":"MISC","tags":[],"title":"Ethernut Download","mime":"text/html","httpstatus":"200","archivestatus":"200"},{"url":"http://lists.egnite.de/mailman/listinfo/en-nut-announce","name":"http://lists.egnite.de/mailman/listinfo/en-nut-announce","refsource":"MISC","tags":[],"title":"En-Nut-Announce Info Page","mime":"text/html","httpstatus":"200","archivestatus":"200"},{"url":"https://www.cisa.gov/news-events/ics-advisories/icsa-21-042-01","name":"https://www.cisa.gov/news-events/ics-advisories/icsa-21-042-01","refsource":"MISC","tags":[],"title":"Multiple Embedded TCP/IP Stacks (Update B) | CISA","mime":"text/html","httpstatus":"200","archivestatus":"200"},{"url":"https://www.forescout.com/resources/numberjack-weak-isn-generation-in-embedded-tcpip-stacks/","name":"https://www.forescout.com/resources/numberjack-weak-isn-generation-in-embedded-tcpip-stacks/","refsource":"MISC","tags":[],"title":"403 Forbidden","mime":"application/pdf","httpstatus":"403","archivestatus":"200"},{"url":"https://www.cve.org/CVERecord?id=CVE-2020-27213","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2020-27213","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[{"cve_year":"2020","cve_id":"27213","vulnerable":"1","versionEndIncluding":"","cpe1":"cpe","cpe2":"2.3","cpe3":"o","cpe4":"ethernut","cpe5":"nut\\/os","cpe6":"5.1","cpe7":"*","cpe8":"*","cpe9":"*","cpe10":"*","cpe11":"*","cpe12":"*","cpe13":"*"}],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"CVE_data_meta":{"ASSIGNER":"cve@mitre.org","ID":"CVE-2020-27213","STATE":"PUBLIC"},"affects":{"vendor":{"vendor_data":[{"product":{"product_data":[{"product_name":"n/a","version":{"version_data":[{"version_value":"n/a"}]}}]},"vendor_name":"n/a"}]}},"data_format":"MITRE","data_type":"CVE","data_version":"4.0","description":{"description_data":[{"lang":"eng","value":"An issue was discovered in Ethernut Nut/OS 5.1. The code that generates Initial Sequence Numbers (ISNs) for TCP connections derives the ISN from an insufficiently random source. As a result, an attacker may be able to determine the ISN of current and future TCP connections and either hijack existing ones or spoof future ones. While the ISN generator seems to adhere to RFC 793 (where a global 32-bit counter is incremented roughly every 4 microseconds), proper ISN generation should aim to follow at least the specifications outlined in RFC 6528."}]},"problemtype":{"problemtype_data":[{"description":[{"lang":"eng","value":"n/a"}]}]},"references":{"reference_data":[{"url":"http://www.ethernut.de/en/download/index.html","refsource":"MISC","name":"http://www.ethernut.de/en/download/index.html"},{"url":"http://lists.egnite.de/mailman/listinfo/en-nut-announce","refsource":"MISC","name":"http://lists.egnite.de/mailman/listinfo/en-nut-announce"},{"refsource":"MISC","name":"https://www.cisa.gov/news-events/ics-advisories/icsa-21-042-01","url":"https://www.cisa.gov/news-events/ics-advisories/icsa-21-042-01"},{"refsource":"MISC","name":"https://www.forescout.com/resources/numberjack-weak-isn-generation-in-embedded-tcpip-stacks/","url":"https://www.forescout.com/resources/numberjack-weak-isn-generation-in-embedded-tcpip-stacks/"}]}},"nvd":{"publishedDate":"2023-10-10 17:15:00","lastModifiedDate":"2023-10-27 19:34:00","problem_types":["CWE-330"],"metrics":{"baseMetricV3":{"cvssV3":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"HIGH","availabilityImpact":"NONE","baseScore":7.5,"baseSeverity":"HIGH"},"exploitabilityScore":3.9,"impactScore":3.6}},"configurations":{"CVE_data_version":"4.0","nodes":[{"operator":"OR","children":[],"cpe_match":[{"vulnerable":true,"cpe23Uri":"cpe:2.3:o:ethernut:nut\\/os:5.1:*:*:*:*:*:*:*","cpe_name":[]}]}]}},"legacy_mitre":{"record":{"CveYear":"2020","CveId":"27213","Ordinal":"188647","Title":"CVE-2020-27213","CVE":"CVE-2020-27213","Year":"2020"},"notes":[{"CveYear":"2020","CveId":"27213","Ordinal":"1","NoteData":"** RESERVED ** This candidate has been reserved by an organization or individual that will use it when announcing a new security problem. When the candidate has been publicized, the details for this candidate will be provided.","Type":"Description","Title":null}]}}}