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

Source: https://junglewise.ai/threats/cve-2026-30963-project-capsule-improper-validation-in-namespace-subresources  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-01. Updated: 2026-06-01  
License: CC BY 4.0 with a link back

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)](https://junglewise.ai/threats/technologies/github-com-projectcapsule-capsule), [Project Capsule Capsule](https://junglewise.ai/threats/technologies/capsule). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Project Capsule](https://junglewise.ai/threats/vendors/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

  ```sh
  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

- [https://github.com/projectcapsule/capsule/releases/tag/v0.13.0](https://github.com/projectcapsule/capsule/releases/tag/v0.13.0)
- [https://github.com/projectcapsule/capsule/security/advisories/GHSA-2ww6-hf35-mfjm](https://github.com/projectcapsule/capsule/security/advisories/GHSA-2ww6-hf35-mfjm)

## Related threats

- [Capsule hostnameRegexHandler parameter order bypass in webhook validation](https://junglewise.ai/threats/cve-2026-61795-capsule-hostnameregexhandler-parameter-order-bypass-in-webhook)
- [Capsule Tenant ForbiddenAnnotations.Regex validation bypass](https://junglewise.ai/threats/cve-2026-61794-capsule-tenant-forbiddenannotations-regex-validation-bypass)
- [Capsule forbidden namespace/service/node label and annotation enforcement bypass](https://junglewise.ai/threats/cve-2026-61672-capsule-forbidden-namespace-service-node-label-and-annotation)
- [Clastix Capsule incorrect authorization via typo in namespaces/finalize webhook](https://junglewise.ai/threats/cve-2026-55636-clastix-capsule-incorrect-authorization-via-typo-in-namespaces)
- [Project Capsule privilege escalation in TenantResource controller](https://junglewise.ai/threats/cve-2026-65835-project-capsule-privilege-escalation-in-tenantresource-controller)