# CVE-2026-55636: Clastix Capsule incorrect authorization via typo in namespaces/finalize webhook

Source: https://junglewise.ai/threats/cve-2026-55636-clastix-capsule-incorrect-authorization-via-typo-in-namespaces  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-15. Updated: 2026-06-17  
License: CC BY 4.0 with a link back

CVE-2026-55636 · Severity: medium · CVSS 5.7 · Published 2026-09-15

Capsule, a multi-tenancy tool for Kubernetes, contains a configuration error that allows users with specific permissions to bypass security restrictions. Due to a typo in the software's validation rules, an attacker could modify protected labels on a namespace, potentially leading to a takeover of tenant resources. This bypasses intended isolation between different users or departments sharing the same cluster.

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

## Quick answers

**Is CVE-2026-55636 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55636 being exploited in the wild.

**How severe is CVE-2026-55636?** Medium severity, with a CVSS score of 5.7, published 15 September 2026.

**Which products and versions are affected?** github.com/projectcapsule/capsule (Go) >= 0.13.0, < 0.13.6, SEMVER:introduced=0.13.0,fixed=0.13.6.

**Is there a fix for CVE-2026-55636?** Yes. github.com/projectcapsule/capsule (Go): upgrade to 0.13.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-55636 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-55636?** Check whether you run github.com/projectcapsule/capsule (Go) 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 0.13.6 or later

  ```sh
  go get github.com/projectcapsule/capsule@v0.13.6
  ```


## Technical details

An incorrect authorization vulnerability exists in Capsule due to a singular/plural typo in the validating webhook configuration. Specifically, the rule uses 'namespace/finalize' instead of the required plural 'namespaces/finalize'. Because Kubernetes admission webhooks match against plural resource names, this typo causes the webhook to ignore requests to the finalize subresource. An attacker with 'namespaces/finalize' RBAC permissions can exploit this to modify namespace labels, such as 'capsule.clastix.io/tenant', bypassing the intended security logic. This issue is an incomplete fix for a previous vulnerability (CVE-2026-30963) and is resolved in version 0.13.6.

## Affected products

- Clastix Capsule >= 0.13.0, < 0.13.6

## Identifiers

- CVE-2026-55636
- GHSA-gwxr-7h77-7777
- GO-2026-5406

## Timeline

- 2026-06-17: advisory: GHSA-gwxr-7h77-7777 published
- 2026-06-17: patched: Fixed in version 0.13.6

## References

- [https://api.github.com/users/character-s](https://api.github.com/users/character-s)
- [https://github.com/character-s](https://github.com/character-s)
- [https://api.github.com/users/character-s/gists%7B/gist_id%7D](https://api.github.com/users/character-s/gists%7B/gist_id%7D)
- [https://api.github.com/users/character-s/repos](https://api.github.com/users/character-s/repos)
- [https://avatars.githubusercontent.com/u/45820854?v=4](https://avatars.githubusercontent.com/u/45820854?v=4)
- [https://api.github.com/users/character-s/events%7B/privacy%7D](https://api.github.com/users/character-s/events%7B/privacy%7D)

## 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)
- [Project Capsule privilege escalation in TenantResource controller](https://junglewise.ai/threats/cve-2026-65835-project-capsule-privilege-escalation-in-tenantresource-controller)
- [Project Capsule Denial of Service via malformed NodeMetadata regex](https://junglewise.ai/threats/cve-2026-65834-project-capsule-denial-of-service-via-malformed-nodemetadata)