{"id":"CVE-2026-20074","aliases":["EUVD-2026-11219","GHSA-95m8-qgxc-hcqx"],"status":"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.\u0026nbsp;\u0026nbsp;","severity":{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00179,"percentile":0.07494,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-1287"],"published":"2026-03-11T16:31:14Z","modified":"2026-07-08T19:07:12Z","products":[{"vendor":"cisco","product":"cisco ios xr software"},{"vendor":"cisco","product":"ios_xr"}],"references":[{"url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-isis-dos-kDMxpSzK","tags":["Mitigation","Vendor Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-20074"},{"url":"https://github.com/advisories/GHSA-95m8-qgxc-hcqx"}],"sources":{"cve":[{"id":"CVE-2026-20074","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.\u0026nbsp;\u0026nbsp;","status":"published","published":"2026-03-11T16:31:14.712Z","modified":"2026-03-11T17:20:21.64Z","cvss":[{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-1287"],"updated_at":"2026-11-02T13:35:55.731353Z"}],"euvd":[{"id":"EUVD-2026-11219","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.\u0026nbsp;\u0026nbsp;","status":"published","published":"2026-03-11T16:31:14Z","modified":"2026-03-11T17:20:21Z","cvss":[{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T19:25:36.762699Z"}],"ghsa":[{"id":"GHSA-95m8-qgxc-hcqx","title":"A vulnerability in the Intermediate System-to-Intermediate System (IS-IS) multi-instance routing...","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.\n\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.\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.\u0026nbsp;\u0026nbsp;","status":"published","published":"2026-03-11T18:30:33Z","modified":"2026-03-11T18:30:40Z","cvss":[{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-1287"],"updated_at":"2026-11-02T15:06:34.428268Z"}],"nvd":[{"id":"CVE-2026-20074","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.\u0026nbsp;\u0026nbsp;","status":"published","published":"2026-03-11T17:16:55.47Z","modified":"2026-07-08T19:07:12.303Z","cvss":[{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-1287"],"updated_at":"2026-11-02T14:12:08.98071Z"}]}}