{"id":"CVE-2026-20038","state":"PUBLISHED","title":"Cisco Nexus 9000 Series Fabric Switches in ACI Mode Policy-Based Redirect Endpoint Group Contract Bypass Vulnerability","description":"A vulnerability in the endpoint group (EPG) contract functionality of Cisco Nexus 9000 Series Fabric Switches in ACI Mode could allow an unauthenticated, remote attacker to bypass configured EPG contracts.\r\n\r\nThis vulnerability is due to an improper control with EPG contracts. An attacker could exploit this vulnerability by sending IPv4 or IPv6 packets using UDP source and destination ports that are assigned to DHCP traffic through an affected device. A successful exploit could allow the attacker to bypass EPG contracts on the affected device.","publishedAt":"2026-10-07T16:11:55.078Z","updatedAt":"2026-10-07T18:05:53.253Z","severity":{"score":5.8,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N","source":"cisco"},"assigner":"cisco","products":["Cisco Cisco NX-OS System Software in ACI Mode"],"affected":[{"vendor":"Cisco","product":"Cisco NX-OS System Software in ACI Mode","defaultStatus":"unknown","versions":[{"version":"15.2(1g)","status":"affected"},{"version":"15.2(2e)","status":"affected"},{"version":"15.2(2f)","status":"affected"},{"version":"15.2(2g)","status":"affected"},{"version":"15.2(2h)","status":"affected"},{"version":"15.2(3f)","status":"affected"},{"version":"15.2(3e)","status":"affected"},{"version":"15.2(3g)","status":"affected"},{"version":"15.2(4d)","status":"affected"},{"version":"15.2(4e)","status":"affected"},{"version":"15.2(5c)","status":"affected"},{"version":"15.2(5d)","status":"affected"},{"version":"16.0(1g)","status":"affected"},{"version":"15.2(5e)","status":"affected"},{"version":"15.2(4f)","status":"affected"},{"version":"15.2(6e)","status":"affected"},{"version":"15.2(6h)","status":"affected"},{"version":"16.0(1j)","status":"affected"},{"version":"15.2(6g)","status":"affected"},{"version":"15.2(7f)","status":"affected"},{"version":"15.2(7g)","status":"affected"},{"version":"16.0(2h)","status":"affected"},{"version":"15.2(8d)","status":"affected"},{"version":"16.0(2j)","status":"affected"},{"version":"15.2(8e)","status":"affected"},{"version":"16.0(3d)","status":"affected"},{"version":"16.0(3e)","status":"affected"},{"version":"15.2(8f)","status":"affected"},{"version":"15.2(8g)","status":"affected"},{"version":"15.3(1d)","status":"affected"},{"version":"15.2(8h)","status":"affected"},{"version":"16.0(4c)","status":"affected"},{"version":"15.3(2a)","status":"affected"},{"version":"15.2(8i)","status":"affected"},{"version":"16.0(5h)","status":"affected"},{"version":"15.3(2b)","status":"affected"},{"version":"16.0(3g)","status":"affected"},{"version":"16.0(5j)","status":"affected"},{"version":"15.3(2c)","status":"affected"},{"version":"16.0(6c)","status":"affected"},{"version":"15.3(2d)","status":"affected"},{"version":"16.1(1f)","status":"affected"},{"version":"16.0(7e)","status":"affected"},{"version":"16.0(8e)","status":"affected"},{"version":"15.3(2e)","status":"affected"},{"version":"16.0(8f)","status":"affected"},{"version":"16.1(2f)","status":"affected"},{"version":"16.1(2g)","status":"affected"},{"version":"15.3(2f)","status":"affected"},{"version":"16.0(9c)","status":"affected"},{"version":"16.1(3f)","status":"affected"},{"version":"16.0(9d)","status":"affected"},{"version":"16.0(6h)","status":"affected"},{"version":"16.0(8h)","status":"affected"},{"version":"16.1(3g)","status":"affected"},{"version":"16.0(9e)","status":"affected"},{"version":"16.1(4h)","status":"affected"},{"version":"16.1(5e)","status":"affected"},{"version":"16.2(1g)","status":"affected"},{"version":"16.0(9f)","status":"affected"},{"version":"16.2(2e)","status":"affected"}]}],"references":["https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-aci-epgcbp-SfDU7NLf"],"weaknesses":["CWE-284"],"ingestedAt":"2026-10-29T20:11:10.572Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/20xxx/CVE-2026-20038.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-20038","state":"PUBLISHED","datePublished":"2026-10-07T16:11:55.078Z","dateUpdated":"2026-10-07T18:05:53.253Z","assignerShortName":"cisco","assignerOrgId":"d1c1063e-7a18-46af-9102-31f8928bc633","dateReserved":"2025-10-08T11:59:15.354Z"},"containers":{"cna":{"title":"Cisco Nexus 9000 Series Fabric Switches in ACI Mode Policy-Based Redirect Endpoint Group Contract Bypass Vulnerability","descriptions":[{"lang":"en","value":"A vulnerability in the endpoint group (EPG) contract functionality of Cisco Nexus 9000 Series Fabric Switches in ACI Mode could allow an unauthenticated, remote attacker to bypass configured EPG contracts.\r\n\r\nThis vulnerability is due to an improper control with EPG contracts. An attacker could exploit this vulnerability by sending IPv4 or IPv6 packets using UDP source and destination ports that are assigned to DHCP traffic through an affected device. A successful exploit could allow the attacker to bypass EPG contracts on the affected device."}],"affected":[{"vendor":"Cisco","product":"Cisco NX-OS System Software in ACI Mode","defaultStatus":"unknown","versions":[{"version":"15.2(1g)","status":"affected"},{"version":"15.2(2e)","status":"affected"},{"version":"15.2(2f)","status":"affected"},{"version":"15.2(2g)","status":"affected"},{"version":"15.2(2h)","status":"affected"},{"version":"15.2(3f)","status":"affected"},{"version":"15.2(3e)","status":"affected"},{"version":"15.2(3g)","status":"affected"},{"version":"15.2(4d)","status":"affected"},{"version":"15.2(4e)","status":"affected"},{"version":"15.2(5c)","status":"affected"},{"version":"15.2(5d)","status":"affected"},{"version":"16.0(1g)","status":"affected"},{"version":"15.2(5e)","status":"affected"},{"version":"15.2(4f)","status":"affected"},{"version":"15.2(6e)","status":"affected"},{"version":"15.2(6h)","status":"affected"},{"version":"16.0(1j)","status":"affected"},{"version":"15.2(6g)","status":"affected"},{"version":"15.2(7f)","status":"affected"},{"version":"15.2(7g)","status":"affected"},{"version":"16.0(2h)","status":"affected"},{"version":"15.2(8d)","status":"affected"},{"version":"16.0(2j)","status":"affected"},{"version":"15.2(8e)","status":"affected"},{"version":"16.0(3d)","status":"affected"},{"version":"16.0(3e)","status":"affected"},{"version":"15.2(8f)","status":"affected"},{"version":"15.2(8g)","status":"affected"},{"version":"15.3(1d)","status":"affected"},{"version":"15.2(8h)","status":"affected"},{"version":"16.0(4c)","status":"affected"},{"version":"15.3(2a)","status":"affected"},{"version":"15.2(8i)","status":"affected"},{"version":"16.0(5h)","status":"affected"},{"version":"15.3(2b)","status":"affected"},{"version":"16.0(3g)","status":"affected"},{"version":"16.0(5j)","status":"affected"},{"version":"15.3(2c)","status":"affected"},{"version":"16.0(6c)","status":"affected"},{"version":"15.3(2d)","status":"affected"},{"version":"16.1(1f)","status":"affected"},{"version":"16.0(7e)","status":"affected"},{"version":"16.0(8e)","status":"affected"},{"version":"15.3(2e)","status":"affected"},{"version":"16.0(8f)","status":"affected"},{"version":"16.1(2f)","status":"affected"},{"version":"16.1(2g)","status":"affected"},{"version":"15.3(2f)","status":"affected"},{"version":"16.0(9c)","status":"affected"},{"version":"16.1(3f)","status":"affected"},{"version":"16.0(9d)","status":"affected"},{"version":"16.0(6h)","status":"affected"},{"version":"16.0(8h)","status":"affected"},{"version":"16.1(3g)","status":"affected"},{"version":"16.0(9e)","status":"affected"},{"version":"16.1(4h)","status":"affected"},{"version":"16.1(5e)","status":"affected"},{"version":"16.2(1g)","status":"affected"},{"version":"16.0(9f)","status":"affected"},{"version":"16.2(2e)","status":"affected"}]}],"references":[{"url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-aci-epgcbp-SfDU7NLf","name":"cisco-sa-aci-epgcbp-SfDU7NLf"}],"metrics":[{"format":"cvssV3_1","cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N","baseScore":5.8,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"NONE","integrityImpact":"LOW","availabilityImpact":"NONE"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-284","lang":"en","description":"Improper Access Control","type":"cwe"}]}],"providerMetadata":{"shortName":"cisco","orgId":"d1c1063e-7a18-46af-9102-31f8928bc633","dateUpdated":"2026-10-07T16:11:55.078Z"},"exploits":[{"lang":"en","value":"The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory."}],"source":{"advisory":"cisco-sa-aci-epgcbp-SfDU7NLf","discovery":"EXTERNAL","defects":["CSCwr18270"]}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-07T18:02:43.242313Z","id":"CVE-2026-20038","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-07T18:05:53.253Z"}}]}}}