CVE-2026-30963: Project Capsule improper validation in namespace subresources

CVE-2026-30963 · Severity: low · CVSS 3.9 · Published 2026-06-01

Capsule is a multi-tenancy framework for Kubernetes that ensures different users or teams (tenants) remain isolated within their own virtual clusters. A security flaw was identified where the system failed to monitor specific administrative sub-channels (subresources) used to update namespace metadata. If a tenant administrator is granted specific permissions by a platform manager, they could exploit this oversight to "hijack" namespaces belonging to other tenants, potentially gaining unauthorized access to resources or disrupting operations.

Technologies: github.com/projectcapsule/capsule (Go), Project Capsule Capsule. Vendors: Go, Project Capsule.

Quick answers

Is CVE-2026-30963 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-30963 being exploited in the wild.
How severe is CVE-2026-30963?
Low severity, with a CVSS score of 3.9, published 1 June 2026.
Which products and versions are affected?
github.com/projectcapsule/capsule (Go) < 0.13.0, SEMVER:introduced=0,fixed=0.13.0; Project Capsule Capsule < 0.13.0.
Is there a fix for CVE-2026-30963?
Yes. github.com/projectcapsule/capsule (Go): upgrade to 0.13.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-30963 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-30963?
Check whether you run github.com/projectcapsule/capsule (Go) or Project Capsule Capsule at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/projectcapsule/capsule (Go): upgrade to 0.13.0 or later
    go get github.com/projectcapsule/capsule@v0.13.0

Technical details

Capsule uses a ValidatingWebhookConfiguration to prevent namespace hijacking by intercepting update and patch operations. However, prior to version 0.13.0, the webhook did not define interception rules for the 'namespace/finalize' and 'namespace/status' subresource APIs. These subresources can be used to modify the metadata field of a namespace, including owner references. An attacker acting as a tenant administrator with RBAC permissions to modify these subresources can patch a namespace's metadata to change its ownership to their own tenant. This bypasses Capsule's multi-tenancy isolation. The issue is fixed in version 0.13.0 by including these subresources in the webhook's interception rules.

Affected products

  • Project Capsule Capsule < 0.13.0

Identifiers

  • CVE-2026-30963
  • GHSA-2ww6-hf35-mfjm
  • GO-2026-5043

Timeline

  • 2026-05-28: patched: Version 0.13.0 released
  • 2026-05-28: advisory: GitHub Security Advisory GHSA-2ww6-hf35-mfjm published
  • 2026-06-01: disclosed: CVE-2026-30963 published to NVD

References

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