CVE-2026-20074

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-20074", "assignerOrgId": "d1c1063e-7a18-46af-9102-31f8928bc633", "state": "PUBLISHED", "assignerShortName": "cisco", "dateReserved": "2025-10-08T11:59:15.362Z", "datePublished": "2026-03-11T16:31:14.712Z", "dateUpdated": "2026-03-11T17:20:21.640Z"}, "containers": {"cna": {"title": "Cisco IOS XR Software Multi-Instance Intermediate System-to-Intermediate System 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 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.  "}], "references": [{"url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-isis-dos-kDMxpSzK", "name": "cisco-sa-isis-dos-kDMxpSzK"}], "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"]}, "problemTypes": [{"descriptions": [{"lang": "en", "description": "Improper Validation of Specified Type of Input", "type": "cwe", "cweId": "CWE-1287"}]}], "affected": [{"vendor": "Cisco", "product": "Cisco IOS XR Software", "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"}], "defaultStatus": "unknown"}], "providerMetadata": {"orgId": "d1c1063e-7a18-46af-9102-31f8928bc633", "shortName": "cisco", "dateUpdated": "2026-03-11T16:31:14.712Z"}}, "adp": [{"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"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-03-11T17:20:21.640Z"}}]}}

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{"affected": [{"affectedData": [{"defaultStatus": "unknown", "product": "Cisco IOS XR Software", "vendor": "Cisco", "versions": [{"status": "affected", "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"}]}], "source": "psirt@cisco.com"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:cisco:ios_xr:*:*:*:*:*:*:*:*", "matchCriteriaId": "8352E25F-6467-4428-B677-013F64C9F130", "versionEndExcluding": "25.2.2", "versionStartIncluding": "7.8.0", "vulnerable": true}, {"criteria": "cpe:2.3:o:cisco:ios_xr:25.3.0:*:*:*:*:*:*:*", "matchCriteriaId": "1B34524C-985A-421D-91D8-3447294A44B3", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "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.  "}, {"lang": "es", "value": "Una vulnerabilidad en la funci\u00f3n de enrutamiento multi-instancia de Intermediate System-to-Intermediate System (IS-IS) de Cisco IOS XR Software podr\u00eda permitir a un atacante no autenticado y adyacente causar que el proceso IS-IS se reinicie inesperadamente.\n\nEsta vulnerabilidad se debe a una validaci\u00f3n de entrada insuficiente de los paquetes IS-IS de entrada. Un atacante podr\u00eda explotar esta vulnerabilidad enviando paquetes IS-IS manipulados a un dispositivo afectado despu\u00e9s de formar una adyacencia. Un exploit exitoso podr\u00eda permitir al atacante causar que el proceso IS-IS se reinicie inesperadamente, lo que resultar\u00eda en una p\u00e9rdida temporal de conectividad a las redes anunciadas y una condici\u00f3n de denegaci\u00f3n de servicio (DoS).\nNota: El protocolo IS-IS es un protocolo de enrutamiento. Para explotar esta vulnerabilidad, un atacante debe ser adyacente en Capa 2 al dispositivo afectado y debe haber formado una adyacencia."}], "id": "CVE-2026-20074", "lastModified": "2026-07-08T19:07:12.303", "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": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-20074", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-03-11T17:04:46.266844Z", "version": "2.0.3"}}]}, "published": "2026-03-11T17:16:55.470", "references": [{"source": "psirt@cisco.com", "tags": ["Mitigation", "Vendor Advisory"], "url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-isis-dos-kDMxpSzK"}], "sourceIdentifier": "psirt@cisco.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-1287"}], "source": "psirt@cisco.com", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "7.8.1"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "7.9.1"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "7.10.1"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "7.8.2"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "7.8.22"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "7.9.2"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "7.11.1"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "7.9.21"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "7.10.2"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.1.1"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "7.11.2"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.2.1"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.1.2"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.2.11"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.3.1"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.4.1"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.2.2"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "7.8.23"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "7.11.21"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.2.20"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.3.2"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.4.10"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "25.1.1"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.4.2"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.3.20"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.4.15"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "25.2.1"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "25.1.2"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.3.30"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.4.30"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "24.2.21"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "25.2.15"}}], "enrichment": {"confidence": 88.0, "confidence_source": "matching", "scores": [{"score": 88.0, "source": "matching"}]}, "original": {"product": "Cisco IOS XR Software", "source": "cna", "vendor": "Cisco"}, "product": "ios_xr_software", "vendor": "cisco"}], "analysis": {"en": {"generated_at": "2026-03-17T15:28:28.889193+00:00", "value": {"mitigation_remediation": ["Verify the Cisco IOS XR Software version and consult the Cisco Security Advisory at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-isis-dos-kDMxpSzK to determine if a patch or firmware update is available.", "Apply the released Cisco patch or firmware update that addresses the IS\u2011IS multi\u2011instance input\u2011validation flaw.", "If a patch cannot be applied immediately, isolate the affected router from the surrounding network or reroute traffic to minimize the impact of a potential denial of service.", "Enable detailed logging of IS\u2011IS adjacency creation and failure events and monitor logs for abnormal packet patterns that could indicate an exploitation attempt."], "summary": {"action": "Patch", "impact": "Denial of Service"}, "threat_synthesis": {"affected_systems": "Affected systems are Cisco IOS XR Software. No specific vulnerable versions are listed in the CNA data, so all releases of this product require checking against Cisco\u2019s official advisory for potential exposure.", "description_and_impact": "Cisco IOS XR Software\u2019s Intermediate System-to-Intermediate System (IS-IS) multi\u2011instance routing feature contains an input\u2011validation flaw in the handling of ingress IS\u2011IS packets, as highlighted by Cisco: a crafted packet can trigger a restart of the IS\u2011IS process, leading to a loss of connectivity to advertised networks and a temporary denial of service. The weakness is classified as CWE\u20111287, a race or state\u2011management error that affects process stability. Key detail from vendor description: \"The vulnerability is due to insufficient input validation of ingress IS\u2011IS packets.\"", "risk_and_exploitability": "CVSS score of 7.4 indicates a high severity. EPSS score of less than 1% suggests a low likelihood of active exploitation. The vulnerability is not in the CISA KEV catalog. Exploitation requires a Layer\u20112 adjacency and an established IS\u2011IS neighbor, after which an attacker can send malformed packets to cause a process reboot. The resulting denial of service can disrupt routing for all advertised networks until the IS\u2011IS process restarts. Key detail from vendor description: \"To exploit this vulnerability, an attacker must be Layer 2\u2011adjacent to the affected device and must have formed an adjacency.\""}}}}, "created": "2026-03-12T09:57:51.944766+00:00", "updated": "2026-03-20T15:30:31.161472+00:00", "vendors": ["cisco", "cisco$PRODUCT$ios_xr_software"]}