{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-20051", "assignerOrgId": "d1c1063e-7a18-46af-9102-31f8928bc633", "state": "PUBLISHED", "assignerShortName": "cisco", "dateReserved": "2025-10-08T11:59:15.355Z", "datePublished": "2026-02-25T16:14:33.859Z", "dateUpdated": "2026-02-25T16:14:33.859Z"}, "containers": {"cna": {"title": "Cisco Nexus 3600-R and 9500-R Series Switching Platforms Layer 2 Loop Denial of Service Vulnerability", "metrics": [{"format": "cvssV3_1", "cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H", "baseScore": 7.4, "baseSeverity": "HIGH", "attackVector": "ADJACENT_NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}}], "descriptions": [{"lang": "en", "value": "A vulnerability with the Ethernet VPN (EVPN) Layer 2 ingress packet processing of Cisco Nexus 3600 Platform Switches and Cisco Nexus 9500-R Series Switching Platforms could allow an unauthenticated, adjacent attacker to trigger a Layer 2 traffic loop.\r\n\r\nThis vulnerability is due to a logic error when processing a crafted Layer 2 ingress frame. An attacker could exploit this vulnerability by sending a stream of crafted Ethernet frames through the targeted device. A successful exploit could allow the attacker to cause a Layer 2 Virtual eXtensible LAN (VxLAN) traffic loop, which, in turn, could result in a denial of service (DoS) condition. This Layer 2 loop could oversubscribe the bandwidth on network interfaces, which would result in all data plane traffic being dropped. To exploit this vulnerability, the attacker must be Layer 2-adjacent to the affected device.\r\nNote: To stop active exploitation of this vulnerability, manual intervention is required to both stop the crafted traffic and flap all involved network interfaces. For additional assistance if a Layer 2 loop that is related to this vulnerability is suspected, contact the Cisco Technical Assistance Center (TAC) or the proper support provider. "}], "references": [{"url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-ether-dos-Kv8YNWZ4", "name": "cisco-sa-nxos-ether-dos-Kv8YNWZ4"}], "exploits": [{"lang": "en", "value": "The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory."}], "source": {"advisory": "cisco-sa-nxos-ether-dos-Kv8YNWZ4", "discovery": "EXTERNAL", "defects": ["CSCwo94451"]}, "problemTypes": [{"descriptions": [{"lang": "en", "description": "Use of Uninitialized Variable", "type": "cwe", "cweId": "CWE-457"}]}], "affected": [{"vendor": "Cisco", "product": "Cisco NX-OS Software", "versions": [{"version": "9.2(3)", "status": "affected"}, {"version": "9.2(2v)", "status": "affected"}, {"version": "9.2(1)", "status": "affected"}, {"version": "9.2(2t)", "status": "affected"}, {"version": "9.2(3y)", "status": "affected"}, {"version": "9.3(2)", "status": "affected"}, {"version": "9.2(4)", "status": "affected"}, {"version": "9.3(1)", "status": "affected"}, {"version": "9.3(1z)", "status": "affected"}, {"version": "9.2(2)", "status": "affected"}, {"version": "9.3(3)", "status": "affected"}, {"version": "9.3(4)", "status": "affected"}, {"version": "9.3(5)", "status": "affected"}, {"version": "9.3(6)", "status": "affected"}, {"version": "9.3(5w)", "status": "affected"}, {"version": "9.3(7)", "status": "affected"}, {"version": "9.3(7k)", "status": "affected"}, {"version": "10.2(1)", "status": "affected"}, {"version": "9.3(7a)", "status": "affected"}, {"version": "9.3(8)", "status": "affected"}, {"version": "10.2(1q)", "status": "affected"}, {"version": "10.2(2)", "status": "affected"}, {"version": "9.3(9)", "status": "affected"}, {"version": "10.2(3)", "status": "affected"}, {"version": "10.2(3t)", "status": "affected"}, {"version": "9.3(10)", "status": "affected"}, {"version": "10.2(2a)", "status": "affected"}, {"version": "10.3(1)", "status": "affected"}, {"version": "10.2(4)", "status": "affected"}, {"version": "10.3(2)", "status": "affected"}, {"version": "9.3(11)", "status": "affected"}, {"version": "10.3(3)", "status": "affected"}, {"version": "10.2(5)", "status": "affected"}, {"version": "9.3(12)", "status": "affected"}, {"version": "10.2(3v)", "status": "affected"}, {"version": "10.4(1)", "status": "affected"}, {"version": "10.2(6)", "status": "affected"}, {"version": "10.3(3w)", "status": "affected"}, {"version": "10.3(3o)", "status": "affected"}, {"version": "10.3(4)", "status": "affected"}, {"version": "10.3(3p)", "status": "affected"}, {"version": "10.3(4a)", "status": "affected"}, {"version": "10.4(2)", "status": "affected"}, {"version": "10.3(3q)", "status": "affected"}, {"version": "9.3(13)", "status": "affected"}, {"version": "10.3(5)", "status": "affected"}, {"version": "10.2(7)", "status": "affected"}, {"version": "10.4(3)", "status": "affected"}, {"version": "10.3(3x)", "status": "affected"}, {"version": "10.3(4g)", "status": "affected"}, {"version": "10.5(1)", "status": "affected"}, {"version": "10.2(8)", "status": "affected"}, {"version": "10.3(3r)", "status": "affected"}, {"version": "10.3(6)", "status": "affected"}, {"version": "9.3(14)", "status": "affected"}, {"version": "10.4(4)", "status": "affected"}, {"version": "10.3(4h)", "status": "affected"}, {"version": "10.5(2)", "status": "affected"}, {"version": "10.3(7)", "status": "affected"}, {"version": "10.4(5)", "status": "affected"}, {"version": "10.5(3)", "status": "affected"}, {"version": "10.2(9)", "status": "affected"}, {"version": "9.3(15)", "status": "affected"}, {"version": "10.4(4g)", "status": "affected"}, {"version": "10.5(4)", "status": "affected"}, {"version": "10.6(1)", "status": "affected"}, {"version": "10.5(3t)", "status": "affected"}, {"version": "10.3(8)", "status": "affected"}, {"version": "10.4(6)", "status": "affected"}, {"version": "10.5(3s)", "status": "affected"}, {"version": "10.5(3e)", "status": "affected"}, {"version": "10.5(3o)", "status": "affected"}, {"version": "9.3(16)", "status": "affected"}, {"version": "10.6(1s)", "status": "affected"}, {"version": "10.5(3p)", "status": "affected"}], "defaultStatus": "unknown"}], "providerMetadata": {"orgId": "d1c1063e-7a18-46af-9102-31f8928bc633", "shortName": "cisco", "dateUpdated": "2026-02-25T16:14:33.859Z"}}}}

{}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "A vulnerability with the Ethernet VPN (EVPN) Layer 2 ingress packet processing of Cisco Nexus 3600 Platform Switches and Cisco Nexus 9500-R Series Switching Platforms could allow an unauthenticated, adjacent attacker to trigger a Layer 2 traffic loop.\r\n\r\nThis vulnerability is due to a logic error when processing a crafted Layer 2 ingress frame. An attacker could exploit this vulnerability by sending a stream of crafted Ethernet frames through the targeted device. A successful exploit could allow the attacker to cause a Layer 2 Virtual eXtensible LAN (VxLAN) traffic loop, which, in turn, could result in a denial of service (DoS) condition. This Layer 2 loop could oversubscribe the bandwidth on network interfaces, which would result in all data plane traffic being dropped. To exploit this vulnerability, the attacker must be Layer 2-adjacent to the affected device.\r\nNote: To stop active exploitation of this vulnerability, manual intervention is required to both stop the crafted traffic and flap all involved network interfaces. For additional assistance if a Layer 2 loop that is related to this vulnerability is suspected, contact the Cisco Technical Assistance Center (TAC) or the proper support provider. "}], "id": "CVE-2026-20051", "lastModified": "2026-02-25T17:25:26.487", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "ADJACENT_NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.4, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "CHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 4.0, "source": "psirt@cisco.com", "type": "Primary"}]}, "published": "2026-02-25T17:25:26.487", "references": [{"source": "psirt@cisco.com", "url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-ether-dos-Kv8YNWZ4"}], "sourceIdentifier": "psirt@cisco.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-457"}], "source": "psirt@cisco.com", "type": "Primary"}]}

{}

{}