{"schema_version":"public-product-v1.1","generated_at":"2026-07-21T10:41:42Z","exposure_verdict":"not_assessed","verdict_reason":"Public evidence does not evaluate exact release, platform, enabled features, configuration, compensating controls, or live exposure.","advisory":{"id":"cisco-sa-nxos-login-blockfor-RwjGVEcu","slug":"cisco-sa-nxos-login-blockfor-rwjgvecu","vendor":"Cisco","title":"Cisco NX-OS Software system login block-for Denial of Service Vulnerability","summary":"A vulnerability in the implementation of the system login block-for command for Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a login process to unexpectedly restart, causing a denial of service (DoS) condition. This vulnerability is due to a logic error in the implementation of the system login block-for command when an attack is detected and acted upon. An attacker could exploit this vulnerability by performing a brute-force login attack on an affected device. A successful exploit could allow the attacker to cause a login process to reload, which could result in a delay during authentication to the affected device. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is available at the following link:https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-login-blockfor-RwjGVEcu This advisory is part of the August 2021 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: August 2021 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication.","severity":"Medium","published_at":"2021-08-25T16:00:00Z","updated_at":"2021-08-25T16:00:00Z","source_url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-login-blockfor-RwjGVEcu","csaf_url":"https://sec.cloudapps.cisco.com/security/center/contentjson/CiscoSecurityAdvisory/cisco-sa-nxos-login-blockfor-RwjGVEcu/csaf/cisco-sa-nxos-login-blockfor-RwjGVEcu.json","exposure_verdict":"not_assessed","verdict_reason":"Public evidence does not evaluate exact release, platform, enabled features, configuration, compensating controls, or live exposure."},"freshness":{"last_source_refreshed_at":"2026-07-21T05:16:34Z","latest_source_refresh_at":"2026-07-21T05:16:34Z","oldest_source_refresh_at":"2026-07-21T03:00:03Z","all_sources_fresh":true,"sources":[{"source":"cisco_advisories","label":"Cisco advisories","last_success_at":"2026-07-21T03:00:03Z","stale":false},{"source":"cisco_csaf","label":"Cisco CSAF","last_success_at":"2026-07-21T05:14:24Z","stale":false},{"source":"nvd_cves","label":"NVD CVEs","last_success_at":"2026-07-21T05:16:30Z","stale":false},{"source":"cisa_kev","label":"CISA KEV","last_success_at":"2026-07-21T05:16:31Z","stale":false},{"source":"first_epss","label":"EPSS","last_success_at":"2026-07-21T05:16:34Z","stale":false}]},"summary":{"cve_count":1,"visible_product_count":5,"public_evidence_count":5,"kev_count":0,"highest_epss":0.01572},"cves":[{"id":"CVE-2021-1590","kev":false,"epss":{"score":0.01572,"percentile":0.7265,"score_date":"2026-07-19","updated_at":"2026-07-20T05:46:48Z"}}],"public_evidence":[{"product":{"name":"Cisco Nexus 5000 Series Switches","slug":"cisco-nexus-5000-series-switches","vendor":"Cisco"},"cve":{"id":"CVE-2021-1590"},"evidence_type":"structured_affected","evidence_label":{"scope":"CSAF product evidence","label":"product_status known affected"},"evidence_source":"Cisco CSAF","source":"Cisco CSAF","source_document_fetched_at":"2026-07-20T04:11:47Z","csaf_status":"known_affected","csaf_product_status":"known_affected","csaf_product_status_path":"vulnerabilities[].product_status.known_affected","raw_product_name":"Cisco NX-OS Software 7.3(0)N1(1) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(0)N1(1a) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(0)N1(1b) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(1)N1(1) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(2)N1(1) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(2)N1(1b) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(2)N1(1c) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(3)N1(1) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(4)N1(1) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(4)N1(1a) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(5)N1(1) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(6)N1(1) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(6)N1(1a) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(7)N1(1) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(7)N1(1a) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(7)N1(1b) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(8)N1(1) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(8)N1(1a) when installed on Cisco Nexus 5000 Series Switches; Cisco NX-OS Software 7.3(8)N1(1b) when installed on Cisco Nexus 5000 Series Switches","exposure_verdict":"not_assessed","verdict_reason":"Public evidence does not evaluate exact release, platform, enabled features, configuration, compensating controls, or live exposure.","exposure_verdict_reason":"Public evidence does not evaluate exact release, platform, enabled features, configuration, compensating controls, or live exposure.","kev":false,"epss":{"score":0.01572,"score_date":"2026-07-19","updated_at":"2026-07-20T05:46:48Z"},"published_at":"2021-08-25T16:00:00Z","updated_at":"2021-08-25T16:00:00Z","advisory_updated_at":"2021-08-25T16:00:00Z","source_url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-login-blockfor-RwjGVEcu","remediation":{"url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-login-blockfor-RwjGVEcu"},"row_display_order":1},{"product":{"name":"Cisco Nexus 6000 Series Switches","slug":"cisco-nexus-6000-series-switches","vendor":"Cisco"},"cve":{"id":"CVE-2021-1590"},"evidence_type":"structured_affected","evidence_label":{"scope":"CSAF product evidence","label":"product_status known affected"},"evidence_source":"Cisco CSAF","source":"Cisco CSAF","source_document_fetched_at":"2026-07-20T04:11:47Z","csaf_status":"known_affected","csaf_product_status":"known_affected","csaf_product_status_path":"vulnerabilities[].product_status.known_affected","raw_product_name":"Cisco NX-OS Software 7.3(0)N1(1) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(0)N1(1a) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(0)N1(1b) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(1)N1(1) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(2)N1(1) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(2)N1(1b) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(2)N1(1c) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(3)N1(1) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(4)N1(1) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(4)N1(1a) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(5)N1(1) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(6)N1(1) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(6)N1(1a) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(7)N1(1) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(7)N1(1a) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(7)N1(1b) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(8)N1(1) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(8)N1(1a) when installed on Cisco Nexus 6000 Series Switches; Cisco NX-OS Software 7.3(8)N1(1b) when installed on Cisco Nexus 6000 Series Switches","exposure_verdict":"not_assessed","verdict_reason":"Public evidence does not evaluate exact release, platform, enabled features, configuration, compensating controls, or live exposure.","exposure_verdict_reason":"Public evidence does not evaluate exact release, platform, enabled features, configuration, compensating controls, or live exposure.","kev":false,"epss":{"score":0.01572,"score_date":"2026-07-19","updated_at":"2026-07-20T05:46:48Z"},"published_at":"2021-08-25T16:00:00Z","updated_at":"2021-08-25T16:00:00Z","advisory_updated_at":"2021-08-25T16:00:00Z","source_url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-login-blockfor-RwjGVEcu","remediation":{"url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-login-blockfor-RwjGVEcu"},"row_display_order":2},{"product":{"name":"Cisco MDS 9000 Multilayer Directors and Fabric Switches","slug":"cisco-mds-9000-multilayer-directors-and-fabric-switches","vendor":"Cisco"},"cve":{"id":"CVE-2021-1590"},"evidence_type":"structured_affected","evidence_label":{"scope":"CSAF product evidence","label":"product_status known affected"},"evidence_source":"Cisco CSAF","source":"Cisco CSAF","source_document_fetched_at":"2026-07-20T04:11:47Z","csaf_status":"known_affected","csaf_product_status":"known_affected","csaf_product_status_path":"vulnerabilities[].product_status.known_affected","raw_product_name":"Cisco NX-OS Software 7.3(0)D1(1) when installed on Cisco MDS 9000 Multilayer Directors and Fabric Switches; Cisco NX-OS Software 7.3(0)DY(1) when installed on Cisco MDS 9000 Multilayer Directors and Fabric Switches; Cisco NX-OS Software 7.3(1)D1(1) when installed on Cisco MDS 9000 Multilayer Directors and Fabric Switches; Cisco NX-OS Software 7.3(1)DY(1) when installed on Cisco MDS 9000 Multilayer Directors and Fabric Switches; Cisco NX-OS Software 8.1(1) when installed on Cisco MDS 9000 Multilayer Directors and Fabric Switches; Cisco NX-OS Software 8.1(1a) when installed on Cisco MDS 9000 Multilayer Directors and Fabric Switches; Cisco NX-OS Software 8.2(1) when installed on Cisco MDS 9000 Multilayer Directors and Fabric Switches; Cisco NX-OS Software 8.2(2) when installed on Cisco MDS 9000 Multilayer Directors and Fabric Switches","exposure_verdict":"not_assessed","verdict_reason":"Public evidence does not evaluate exact release, platform, enabled features, configuration, compensating controls, or live exposure.","exposure_verdict_reason":"Public evidence does not evaluate exact release, platform, enabled features, configuration, compensating controls, or live exposure.","kev":false,"epss":{"score":0.01572,"score_date":"2026-07-19","updated_at":"2026-07-20T05:46:48Z"},"published_at":"2021-08-25T16:00:00Z","updated_at":"2021-08-25T16:00:00Z","advisory_updated_at":"2021-08-25T16:00:00Z","source_url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-login-blockfor-RwjGVEcu","remediation":{"url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-login-blockfor-RwjGVEcu"},"row_display_order":3},{"product":{"name":"Cisco Nexus 7000 Series Switches","slug":"cisco-nexus-7000-series-switches","vendor":"Cisco"},"cve":{"id":"CVE-2021-1590"},"evidence_type":"structured_affected","evidence_label":{"scope":"CSAF product evidence","label":"product_status known affected"},"evidence_source":"Cisco CSAF","source":"Cisco CSAF","source_document_fetched_at":"2026-07-20T04:11:47Z","csaf_status":"known_affected","csaf_product_status":"known_affected","csaf_product_status_path":"vulnerabilities[].product_status.known_affected","raw_product_name":"Cisco NX-OS Software 7.3(0)D1(1) when installed on Cisco Nexus 7000 Series Switches; Cisco NX-OS Software 7.3(0)DX(1) when installed on Cisco Nexus 7000 Series Switches; Cisco NX-OS Software 7.3(1)D1(1) when installed on Cisco Nexus 7000 Series Switches; Cisco NX-OS Software 7.3(2)D1(1) when installed on Cisco Nexus 7000 Series Switches; Cisco NX-OS Software 7.3(2)D1(2) when installed on Cisco Nexus 7000 Series Switches; Cisco NX-OS Software 7.3(2)D1(3) when installed on Cisco Nexus 7000 Series Switches; Cisco NX-OS Software 7.3(2)D1(3a) when installed on Cisco Nexus 7000 Series Switches; Cisco NX-OS Software 8.1(1) when installed on Cisco Nexus 7000 Series Switches; Cisco NX-OS Software 8.1(2) when installed on Cisco Nexus 7000 Series Switches; Cisco NX-OS Software 8.1(2a) when installed on Cisco Nexus 7000 Series Switches; Cisco NX-OS Software 8.2(1) when installed on Cisco Nexus 7000 Series Switches; Cisco NX-OS Software 8.2(2) when installed on Cisco Nexus 7000 Series Switches","exposure_verdict":"not_assessed","verdict_reason":"Public evidence does not evaluate exact release, platform, enabled features, configuration, compensating controls, or live exposure.","exposure_verdict_reason":"Public evidence does not evaluate exact release, platform, enabled features, configuration, compensating controls, or live exposure.","kev":false,"epss":{"score":0.01572,"score_date":"2026-07-19","updated_at":"2026-07-20T05:46:48Z"},"published_at":"2021-08-25T16:00:00Z","updated_at":"2021-08-25T16:00:00Z","advisory_updated_at":"2021-08-25T16:00:00Z","source_url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-login-blockfor-RwjGVEcu","remediation":{"url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-login-blockfor-RwjGVEcu"},"row_display_order":4},{"product":{"name":"Cisco Unified Computing System (Managed)","slug":"cisco-unified-computing-system-managed","vendor":"Cisco"},"cve":{"id":"CVE-2021-1590"},"evidence_type":"structured_affected","evidence_label":{"scope":"CSAF product evidence","label":"product_status known affected"},"evidence_source":"Cisco CSAF","source":"Cisco CSAF","source_document_fetched_at":"2026-07-20T04:11:47Z","csaf_status":"known_affected","csaf_product_status":"known_affected","csaf_product_status_path":"vulnerabilities[].product_status.known_affected","raw_product_name":"Cisco Unified Computing System (Managed)","exposure_verdict":"not_assessed","verdict_reason":"Public evidence does not evaluate exact release, platform, enabled features, configuration, compensating controls, or live exposure.","exposure_verdict_reason":"Public evidence does not evaluate exact release, platform, enabled features, configuration, compensating controls, or live exposure.","kev":false,"epss":{"score":0.01572,"score_date":"2026-07-19","updated_at":"2026-07-20T05:46:48Z"},"published_at":"2021-08-25T16:00:00Z","updated_at":"2021-08-25T16:00:00Z","advisory_updated_at":"2021-08-25T16:00:00Z","source_url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-login-blockfor-RwjGVEcu","remediation":{"url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-login-blockfor-RwjGVEcu"},"row_display_order":5}]}