Vulnerability-Lookup

GHSA-35C7-W35F-XWGH

Vulnerability from github – Published: 2023-10-30 03:30 – Updated: 2026-07-06 16:26

Summary

Kube-proxy may unintentionally forward traffic

Details

Kube-proxy on Windows can unintentionally forward traffic to local processes listening on the same port (spec.ports[*].port) as a LoadBalancer Service when the LoadBalancer controller does not set the status.loadBalancer.ingress[].ip field. Clusters where the LoadBalancer controller sets the status.loadBalancer.ingress[].ip field are unaffected.

Severity

5.8 (Medium)


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

Show details on source website

JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "k8s.io/kubernetes"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.21.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2021-25736"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": true,
    "github_reviewed_at": "2023-10-31T22:23:04Z",
    "nvd_published_at": "2023-10-30T03:15:07Z",
    "severity": "MODERATE"
  },
  "details": "Kube-proxy on Windows can unintentionally forward traffic to local processes listening on the same port (`spec.ports[*].port`) as a LoadBalancer Service when the LoadBalancer controller does not set the `status.loadBalancer.ingress[].ip` field. Clusters \nwhere the LoadBalancer controller sets the `status.loadBalancer.ingress[].ip` field are unaffected.",
  "id": "GHSA-35c7-w35f-xwgh",
  "modified": "2026-07-06T16:26:45Z",
  "published": "2023-10-30T03:30:15Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-25736"
    },
    {
      "type": "WEB",
      "url": "https://github.com/kubernetes/kubernetes/pull/99958"
    },
    {
      "type": "WEB",
      "url": "https://github.com/kubernetes/kubernetes/commit/b014610de3e5cf1bb0f7844b5758d29fc18b75e6"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/kubernetes/kubernetes"
    },
    {
      "type": "WEB",
      "url": "https://groups.google.com/g/kubernetes-security-announce/c/lIoOPObO51Q/m/O15LOazPAgAJ"
    },
    {
      "type": "WEB",
      "url": "https://security.netapp.com/advisory/ntap-20231221-0003"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Kube-proxy may unintentionally forward traffic"
}

CVE-2021-25736 (GCVE-0-2021-25736)

Vulnerability from cvelistv5 – Published: 2023-10-30 02:19 – Updated: 2025-06-12 14:42

Title

Windows kube-proxy LoadBalancer contention

Summary

Kube-proxy on Windows can unintentionally forward traffic to local processes listening on the same port (“spec.ports[*].port”) as a LoadBalancer Service when the LoadBalancer controller does not set the “status.loadBalancer.ingress[].ip” field. Clusters where the LoadBalancer controller sets the “status.loadBalancer.ingress[].ip” field are unaffected.

Severity

5.8 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2025-06-12 14:39 UTC

CWE

CWE-114 - Process Control

Assigner

kubernetes mitre root

References

3 references

URL	Tags
https://github.com/kubernetes/kubernetes/pull/99958
https://groups.google.com/g/kubernetes-security-a…
https://security.netapp.com/advisory/ntap-2023122…

Impacted products

1 product

Vendor	Product	Version
Kubernetes	Kubernetes	Affected: 0 , ≤ v1.20.5 (v1.20.5)

Credits

Eric Paris Christian Hernandez

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2024-08-03T20:11:28.044Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "tags": [
              "x_transferred"
            ],
            "url": "https://github.com/kubernetes/kubernetes/pull/99958"
          },
          {
            "tags": [
              "x_transferred"
            ],
            "url": "https://groups.google.com/g/kubernetes-security-announce/c/lIoOPObO51Q/m/O15LOazPAgAJ"
          },
          {
            "tags": [
              "x_transferred"
            ],
            "url": "https://security.netapp.com/advisory/ntap-20231221-0003/"
          }
        ],
        "title": "CVE Program Container"
      },
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2021-25736",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2025-06-12T14:39:48.612391Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-114",
                "description": "CWE-114 Process Control",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2025-06-12T14:42:12.231Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "modules": [
            "Kube-Proxy"
          ],
          "platforms": [
            "Windows"
          ],
          "product": "Kubernetes",
          "repo": "https://github.com/kubernetes/kubernetes",
          "vendor": "Kubernetes",
          "versions": [
            {
              "lessThanOrEqual": "v1.20.5",
              "status": "affected",
              "version": "0",
              "versionType": "v1.20.5"
            }
          ]
        }
      ],
      "credits": [
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          "lang": "en",
          "type": "finder",
          "user": "00000000-0000-4000-9000-000000000000",
          "value": "Eric Paris"
        },
        {
          "lang": "en",
          "type": "finder",
          "user": "00000000-0000-4000-9000-000000000000",
          "value": "Christian Hernandez"
        }
      ],
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          "lang": "en",
          "supportingMedia": [
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          ],
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        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.8,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "NONE",
            "privilegesRequired": "HIGH",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:N/A:N",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
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        }
      ],
      "providerMetadata": {
        "dateUpdated": "2023-12-21T22:06:17.289Z",
        "orgId": "a6081bf6-c852-4425-ad4f-a67919267565",
        "shortName": "kubernetes"
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        {
          "url": "https://groups.google.com/g/kubernetes-security-announce/c/lIoOPObO51Q/m/O15LOazPAgAJ"
        },
        {
          "url": "https://security.netapp.com/advisory/ntap-20231221-0003/"
        }
      ],
      "solutions": [
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            }
          ],
          "value": "This issue has been fixed in the following versions:\n\n\n\n  *  \nv1.21.0\n  *  \nv1.20.6\n  *  \nv1.19.10\n  *  \nv1.18.18"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
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      "title": "Windows kube-proxy LoadBalancer contention",
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      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a6081bf6-c852-4425-ad4f-a67919267565",
    "assignerShortName": "kubernetes",
    "cveId": "CVE-2021-25736",
    "datePublished": "2023-10-30T02:19:48.916Z",
    "dateReserved": "2021-01-21T21:42:58.237Z",
    "dateUpdated": "2025-06-12T14:42:12.231Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1"
}

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-35C7-W35F-XWGH

CVE-2021-25736 (GCVE-0-2021-25736)

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