{"id":"CVE-2026-20074","title":"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\nTh…","summary":"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\nTh…","severity":"high","cvss":7.4,"cvssVector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","cwe":["CWE-1287"],"vendor":"cisco","product":"ios_xr","affected":["ios_xr >= 7.8.0, < 25.2.2","ios_xr = 25.3.0"],"patched":["ios_xr 25.2.2"],"published":"2026-03-11","updated":"2026-07-08","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-20074","references":[{"url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-isis-dos-kDMxpSzK","label":"psirt@cisco.com"}],"tags":["nvd"],"epss":0.0016,"epssPercentile":0.05576,"ingestedAt":"2026-07-08T19:46:17.205Z","slug":"CVE-2026-20074","body":"## Overview\n\nA 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.&nbsp;&nbsp;\n\n## Affected\n\n- `ios_xr >= 7.8.0, < 25.2.2`\n- `ios_xr = 25.3.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `ios_xr 25.2.2`","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":40.7,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}