{"id":"CVE-2026-20074","state":"PUBLISHED","title":"Cisco IOS XR Software Multi-Instance Intermediate System-to-Intermediate System Denial of Service Vulnerability","description":"A vulnerability in the Intermediate System-to-Intermediate System (IS-IS) multi-instance routing feature of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause the IS-IS process to restart unexpectedly.\r\n\r\nThis vulnerability is due to insufficient input validation of ingress IS-IS packets. An attacker could exploit this vulnerability by sending crafted IS-IS packets to an affected device after forming an adjacency. A successful exploit could allow the attacker to cause the IS-IS process to restart unexpectedly, resulting in a temporary loss of connectivity to advertised networks and a denial of service (DoS) condition.\r\nNote: The IS-IS protocol is a routing protocol. To exploit this vulnerability, an attacker must be Layer 2-adjacent to the affected device and must have formed an adjacency.  ","publishedAt":"2026-03-11T16:31:14.712Z","updatedAt":"2026-03-11T17:20:21.640Z","severity":{"score":7.4,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","source":"cisco"},"assigner":"cisco","products":["Cisco Cisco IOS XR Software"],"affected":[{"vendor":"Cisco","product":"Cisco IOS XR Software","defaultStatus":"unknown","versions":[{"version":"7.8.1","status":"affected"},{"version":"7.9.1","status":"affected"},{"version":"7.10.1","status":"affected"},{"version":"7.8.2","status":"affected"},{"version":"7.8.22","status":"affected"},{"version":"7.9.2","status":"affected"},{"version":"7.11.1","status":"affected"},{"version":"7.9.21","status":"affected"},{"version":"7.10.2","status":"affected"},{"version":"24.1.1","status":"affected"},{"version":"7.11.2","status":"affected"},{"version":"24.2.1","status":"affected"},{"version":"24.1.2","status":"affected"},{"version":"24.2.11","status":"affected"},{"version":"24.3.1","status":"affected"},{"version":"24.4.1","status":"affected"},{"version":"24.2.2","status":"affected"},{"version":"7.8.23","status":"affected"},{"version":"7.11.21","status":"affected"},{"version":"24.2.20","status":"affected"},{"version":"24.3.2","status":"affected"},{"version":"24.4.10","status":"affected"},{"version":"25.1.1","status":"affected"},{"version":"24.4.2","status":"affected"},{"version":"24.3.20","status":"affected"},{"version":"24.4.15","status":"affected"},{"version":"25.2.1","status":"affected"},{"version":"25.1.2","status":"affected"},{"version":"24.3.30","status":"affected"},{"version":"24.4.30","status":"affected"},{"version":"24.2.21","status":"affected"},{"version":"25.2.15","status":"affected"}]}],"references":["https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-isis-dos-kDMxpSzK"],"weaknesses":["CWE-1287"],"ingestedAt":"2026-10-29T20:11:10.572Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/20xxx/CVE-2026-20074.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-20074","state":"PUBLISHED","datePublished":"2026-03-11T16:31:14.712Z","dateUpdated":"2026-03-11T17:20:21.640Z","assignerShortName":"cisco","assignerOrgId":"d1c1063e-7a18-46af-9102-31f8928bc633","dateReserved":"2025-10-08T11:59:15.362Z"},"containers":{"cna":{"title":"Cisco IOS XR Software Multi-Instance Intermediate System-to-Intermediate System Denial of Service Vulnerability","descriptions":[{"lang":"en","value":"A vulnerability in the Intermediate System-to-Intermediate System (IS-IS) multi-instance routing feature of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause the IS-IS process to restart unexpectedly.\r\n\r\nThis vulnerability is due to insufficient input validation of ingress IS-IS packets. An attacker could exploit this vulnerability by sending crafted IS-IS packets to an affected device after forming an adjacency. A successful exploit could allow the attacker to cause the IS-IS process to restart unexpectedly, resulting in a temporary loss of connectivity to advertised networks and a denial of service (DoS) condition.\r\nNote: The IS-IS protocol is a routing protocol. To exploit this vulnerability, an attacker must be Layer 2-adjacent to the affected device and must have formed an adjacency.  "}],"affected":[{"vendor":"Cisco","product":"Cisco IOS XR Software","defaultStatus":"unknown","versions":[{"version":"7.8.1","status":"affected"},{"version":"7.9.1","status":"affected"},{"version":"7.10.1","status":"affected"},{"version":"7.8.2","status":"affected"},{"version":"7.8.22","status":"affected"},{"version":"7.9.2","status":"affected"},{"version":"7.11.1","status":"affected"},{"version":"7.9.21","status":"affected"},{"version":"7.10.2","status":"affected"},{"version":"24.1.1","status":"affected"},{"version":"7.11.2","status":"affected"},{"version":"24.2.1","status":"affected"},{"version":"24.1.2","status":"affected"},{"version":"24.2.11","status":"affected"},{"version":"24.3.1","status":"affected"},{"version":"24.4.1","status":"affected"},{"version":"24.2.2","status":"affected"},{"version":"7.8.23","status":"affected"},{"version":"7.11.21","status":"affected"},{"version":"24.2.20","status":"affected"},{"version":"24.3.2","status":"affected"},{"version":"24.4.10","status":"affected"},{"version":"25.1.1","status":"affected"},{"version":"24.4.2","status":"affected"},{"version":"24.3.20","status":"affected"},{"version":"24.4.15","status":"affected"},{"version":"25.2.1","status":"affected"},{"version":"25.1.2","status":"affected"},{"version":"24.3.30","status":"affected"},{"version":"24.4.30","status":"affected"},{"version":"24.2.21","status":"affected"},{"version":"25.2.15","status":"affected"}]}],"references":[{"url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-isis-dos-kDMxpSzK","name":"cisco-sa-isis-dos-kDMxpSzK"}],"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"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-1287","lang":"en","description":"Improper Validation of Specified Type of Input","type":"cwe"}]}],"providerMetadata":{"shortName":"cisco","orgId":"d1c1063e-7a18-46af-9102-31f8928bc633","dateUpdated":"2026-03-11T16:31:14.712Z"},"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-isis-dos-kDMxpSzK","discovery":"INTERNAL","defects":["CSCwq71827"]}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-20074","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-03-11T17:04:46.266844Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-03-11T17:20:21.640Z"}}]}}}