# CVE-2026-30963: Capsule Namespace Hijacking via subresource

> Tenant administrators can hijack namespaces by exploiting missing webhook validation on namespace subresources, leading to unauthorized privilege escalation and data modification.

- **Severity:** Low 3.9 (`CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 1 Jun 2026
- **Updated:** 2 Jun 2026
- **Also known as:** GHSA-2ww6-hf35-mfjm, GO-2026-5043

## What is CVE-2026-30963?

CVE-2026-30963 is a low-severity missing authorization vulnerability in projectcapsule capsule, published on 1 Jun 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.

### Official description

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.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-30963?

3 open source packages ship an affected version, including github.com/projectcapsule/capsule. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/projectcapsule/capsule` | Go | All versions | 0.13.0 |
| `github.com/projectcapsule/capsule` | Go | All versions | 0.13.0 |
| `github.com/projectcapsule/capsule` | Go | All versions | 0.13.0 |

Products: Projectcapsule Capsule.

## How do I fix CVE-2026-30963?

Upgrade github.com/projectcapsule/capsule to 0.13.0 or later.

## Is CVE-2026-30963 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-30963 exists.

## Other vulnerabilities in projectcapsule capsule

- [CVE-2024-39690](https://insights.sbomify.com/CVE-2024-39690/): Capsule tenant owner with "patch namespace" permission can hijack system namespaces (high 8.5)
- [CVE-2026-22872](https://insights.sbomify.com/CVE-2026-22872/): Capsule TenantResource RawItems Cluster-Scoped Resource Creation Vulnerability (medium 6.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-30963 and fix it if it is affected.

What it is: CVE-2026-30963 is a low-severity missing authorization vulnerability in projectcapsule capsule, published on 1 Jun 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-30963 exists.

Affected packages and fixed versions:
- github.com/projectcapsule/capsule (Go): affected all versions; fixed in 0.13.0
- github.com/projectcapsule/capsule (Go): affected all versions; fixed in 0.13.0
- github.com/projectcapsule/capsule (Go): affected all versions; fixed in 0.13.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-30963/ (Markdown: https://insights.sbomify.com/CVE-2026-30963/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-30963
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-30963
- OSV: https://osv.dev/vulnerability/CVE-2026-30963

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-30963/
Summaries are generated and may contain mistakes; the official description above is the record.