FKIE_CVE-2026-20074
Vulnerability from fkie_nvd - Published: 2026-03-11 17:16 - Updated: 2026-07-08 19:07
Severity
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.
This 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.
Note: 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 | Tags | ||
|---|---|---|---|
| psirt@cisco.com | https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-isis-dos-kDMxpSzK | Mitigation, Vendor Advisory |
{
"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.\u0026nbsp;\u0026nbsp;"
},
{
"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"
}
]
}
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Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
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- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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