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GHSA-H75F-8F3X-9M8C

Vulnerability from github – Published: 2026-05-20 18:31 – Updated: 2026-05-20 18:31

Details

This vulnerability is due to incorrect parsing of a transitive BGP attribute. An attacker could exploit this vulnerability by sending a crafted BGP update through an established BGP peer session. If the update propagates to an affected device, it could cause the device to drop the BGP session and flap with the BGP peer that is forwarding this update, resulting in a DoS condition.

Severity

6.8 (Medium)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-20171"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-670"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-20T17:16:19Z",
    "severity": "MODERATE"
  },
  "details": "A vulnerability in the Border Gateway Protocol (BGP)\u0026nbsp;enforce-first-as feature of\u0026nbsp;Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode could allow an unauthenticated, remote attacker to trigger BGP peer flaps, resulting in a denial of service (DoS) condition.\n\nThis vulnerability is due to incorrect parsing of a transitive BGP attribute. An attacker could exploit this vulnerability by sending a crafted BGP update through an established BGP peer session. If the update propagates to an affected device, it could cause the device to drop the BGP session and flap with the BGP peer that is forwarding this update, resulting in a DoS condition.",
  "id": "GHSA-h75f-8f3x-9m8c",
  "modified": "2026-05-20T18:31:35Z",
  "published": "2026-05-20T18:31:35Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-20171"
    },
    {
      "type": "WEB",
      "url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-bgp-iefab-3hb2pwtx"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-20171 (GCVE-0-2026-20171)

Vulnerability from cvelistv5 – Published: 2026-05-20 16:06 – Updated: 2026-05-20 18:31

Title

Cisco Nexus 3000 and 9000 Series Border Gateway Protocol Denial of Service Vulnerability

Summary

A vulnerability in the Border Gateway Protocol (BGP) enforce-first-as feature of Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode could allow an unauthenticated, remote attacker to trigger BGP peer flaps, resulting in a denial of service (DoS) condition. This vulnerability is due to incorrect parsing of a transitive BGP attribute. An attacker could exploit this vulnerability by sending a crafted BGP update through an established BGP peer session. If the update propagates to an affected device, it could cause the device to drop the BGP session and flap with the BGP peer that is forwarding this update, resulting in a DoS condition.

Severity

6.8 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-05-20 18:31 UTC

CWE

CWE-670 - Always-Incorrect Control Flow Implementation

Assigner

cisco mitre root Scorecard

References

1 reference

URL	Tags
https://sec.cloudapps.cisco.com/security/center/c…

Impacted products

1 product

Vendor	Product	Version
Cisco	Cisco NX-OS Software	Affected: 10.2(1) Affected: 10.2(1q) Affected: 10.2(2) Affected: 10.2(3) Affected: 10.2(3t) Affected: 10.2(2a) Affected: 10.3(1) Affected: 10.2(4) Affected: 10.3(2) Affected: 10.3(3) Affected: 10.2(5) Affected: 10.2(3v) Affected: 10.4(1) Affected: 10.3(99w) Affected: 10.2(6) Affected: 10.3(3w) Affected: 10.3(99x) Affected: 10.3(3o) Affected: 10.3(4) Affected: 10.3(3p) Affected: 10.3(4a) Affected: 10.4(2) Affected: 10.3(3q) Affected: 10.3(5) Affected: 10.2(7) Affected: 10.4(3) Affected: 10.3(3x) Affected: 10.3(4g) Affected: 10.5(1) Affected: 10.2(8) Affected: 10.3(3r) Affected: 10.3(6) Affected: 10.4(4) Affected: 10.3(4h) Affected: 10.5(2) Affected: 10.3(7) Affected: 10.4(5) Affected: 10.5(3) Affected: 10.2(9) Affected: 10.4(4g) Affected: 10.6(1) Affected: 10.5(3t) Affected: 10.3(8) Affected: 10.4(6) Affected: 10.5(3s) Affected: 10.5(3e) Affected: 10.5(3o) Affected: 10.6(1s) Affected: 10.5(3p)

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-20171",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-20T18:31:37.215391Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
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        "providerMetadata": {
          "dateUpdated": "2026-05-20T18:31:44.204Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
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      "affected": [
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          "defaultStatus": "unknown",
          "product": "Cisco NX-OS Software",
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              "version": "10.2(1)"
            },
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              "status": "affected",
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              "status": "affected",
              "version": "10.2(3t)"
            },
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              "status": "affected",
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              "status": "affected",
              "version": "10.3(1)"
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              "status": "affected",
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            },
            {
              "status": "affected",
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            },
            {
              "status": "affected",
              "version": "10.2(5)"
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              "status": "affected",
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              "status": "affected",
              "version": "10.3(99w)"
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            {
              "status": "affected",
              "version": "10.2(6)"
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              "status": "affected",
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              "status": "affected",
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            {
              "status": "affected",
              "version": "10.3(4a)"
            },
            {
              "status": "affected",
              "version": "10.4(2)"
            },
            {
              "status": "affected",
              "version": "10.3(3q)"
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            {
              "status": "affected",
              "version": "10.3(5)"
            },
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              "status": "affected",
              "version": "10.2(7)"
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              "version": "10.4(3)"
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            {
              "status": "affected",
              "version": "10.3(3x)"
            },
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            },
            {
              "status": "affected",
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            },
            {
              "status": "affected",
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            },
            {
              "status": "affected",
              "version": "10.4(4)"
            },
            {
              "status": "affected",
              "version": "10.3(4h)"
            },
            {
              "status": "affected",
              "version": "10.5(2)"
            },
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              "status": "affected",
              "version": "10.3(7)"
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              "status": "affected",
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            {
              "status": "affected",
              "version": "10.5(3)"
            },
            {
              "status": "affected",
              "version": "10.2(9)"
            },
            {
              "status": "affected",
              "version": "10.4(4g)"
            },
            {
              "status": "affected",
              "version": "10.6(1)"
            },
            {
              "status": "affected",
              "version": "10.5(3t)"
            },
            {
              "status": "affected",
              "version": "10.3(8)"
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            {
              "status": "affected",
              "version": "10.4(6)"
            },
            {
              "status": "affected",
              "version": "10.5(3s)"
            },
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              "status": "affected",
              "version": "10.5(3e)"
            },
            {
              "status": "affected",
              "version": "10.5(3o)"
            },
            {
              "status": "affected",
              "version": "10.6(1s)"
            },
            {
              "status": "affected",
              "version": "10.5(3p)"
            }
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      ],
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          "lang": "en",
          "value": "A vulnerability in the Border Gateway Protocol (BGP)\u0026nbsp;enforce-first-as feature of\u0026nbsp;Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode could allow an unauthenticated, remote attacker to trigger BGP peer flaps, resulting in a denial of service (DoS) condition.\r\n\r\nThis vulnerability is due to incorrect parsing of a transitive BGP attribute. An attacker could exploit this vulnerability by sending a crafted BGP update through an established BGP peer session. If the update propagates to an affected device, it could cause the device to drop the BGP session and flap with the BGP peer that is forwarding this update, resulting in a DoS condition."
        }
      ],
      "exploits": [
        {
          "lang": "en",
          "value": "The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory."
        }
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      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 6.8,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H",
            "version": "3.1"
          },
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        }
      ],
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        {
          "descriptions": [
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      "providerMetadata": {
        "dateUpdated": "2026-05-20T16:06:38.711Z",
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        }
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        "defects": [
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      "title": "Cisco Nexus 3000 and 9000 Series Border Gateway Protocol Denial of Service Vulnerability"
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    "state": "PUBLISHED"
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  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
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.

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.

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GHSA-H75F-8F3X-9M8C

CVE-2026-20171 (GCVE-0-2026-20171)

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