CVE-2026-55636
Received Received - Intake

Privilege Escalation in Capsule Kubernetes Framework

Publication date: 2026-09-15

Last updated on: 2026-09-15

Assigner: GitHub, Inc.

Description
Capsule is a multi-tenancy and policy-based framework for Kubernetes. From 0.13.0 until 0.13.6, charts/capsule/templates/configuration.yaml configures the validating webhook with namespace/finalize instead of the Kubernetes resource name namespaces/finalize. A user with namespaces/finalize RBAC can send a PUT request to /api/v1/namespaces/{namespace}/finalize, and the singular rule never matches the plural resource, so the validating webhook is not invoked and the user can change the namespace tenant label. matchPolicy: Equivalent does not compensate because it handles API group and version equivalence rather than resource-name errors. This vulnerability is fixed in 0.13.6.

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Meta Information

Published
2026-09-15
Last Modified
2026-09-15
Generated
2026-09-15
AI Q&A
2026-09-15
EPSS Evaluated
N/A
NVD
CVE-2026-55636
EUVD
EUVD-2026-78670

Affected Vendors & Products

Showing 5 associated CPEs
Vendor Product Version / Range
projectcapsule capsule From 0.13.0 (inc) to 0.13.6 (inc)
projectcapsule capsule 0.13.6
projectcapsule capsule From 0.13.2 (inc) to 0.13.6 (exc)
capsule capsule From 0.13.0 (inc) to 0.13.6 (inc)
capsule capsule 0.13.6

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-863 The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

Attack-Flow Graph

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Executive Summary

CVE-2026-55636 is a vulnerability in Capsule, a Kubernetes multi-tenancy framework. It involves a typo in the Helm chart configuration where 'namespace/finalize' (singular) was used instead of the correct plural form 'namespaces/finalize'. This prevents the validating webhook from triggering for finalize operations, allowing users with limited RBAC permissions to bypass security controls and modify namespace tenant labels.

Detection Guidance

Check Capsule version with 'helm list -n capsule-system' or 'kubectl get pods -n capsule-system -l app=capsule'. Verify webhook configuration in Helm values or 'kubectl get validatingwebhookconfiguration'. Look for 'namespace/finalize' in configuration.yaml files.

Impact Analysis

An attacker with namespaces/finalize RBAC permissions could exploit this to change namespace tenant labels, effectively hijacking namespace ownership. This could lead to unauthorized access or manipulation of resources within those namespaces, compromising the integrity of the Kubernetes cluster's multi-tenancy model.

Compliance Impact

This vulnerability could impact compliance by allowing unauthorized modifications to namespace labels, potentially leading to unauthorized access to sensitive data. This may violate data protection requirements under GDPR or HIPAA, depending on the data stored in the affected namespaces.

Mitigation Strategies

Upgrade to Capsule v0.13.6 or later. Update Helm chart values to use 'namespaces/finalize' instead of 'namespace/finalize'. Verify webhook rules are correctly configured to trigger on finalize operations.

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