Capsule tenant owners with "patch namespace" permission can hijack system namespaces label

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.0 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H

EPSS

• CVE-2025-55205: 0.46% estimated exploitation activity in the next 30 days; percentile 39.88 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A namespace label injection vulnerability in Capsule v0.10.3 allows authenticated tenant users to inject arbitrary labels into system namespaces (kube-system, default, capsule-system), bypassing multi-tenant isolation and potentially accessing cross-tenant resources through TenantResource selectors. This vulnerability enables privilege escalation and violates the fundamental security boundaries that Capsule is designed to enforce. Details The vulnerability exists in the namespace validation webhook logic located in pkg/webhook/namespace/validation/patch.go:60-77. The critical flaw is in the conditional check that only validates tenant ownership when a namespace already has a tenant label: Root Cause Analysis: 1. Missing Default Protection: System namespaces (kube-system, default, capsule-system) do not have the capsule.clastix.io/tenant label by default 2. Bypass Logic: The webhook only enforces tenant ownership validation when the target namespace already belongs to a tenant…

Published by the source

18 Aug 2025, 21:00 UTC

Last modified by the source

29 Aug 2025, 20:35 UTC

Source last checked

26 Oct 2026, 15:10 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-fcpm-6mxq-m5vv

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# Patch Next advisory brief: CVE-2025-55205

Advisory: Capsule tenant owners with "patch namespace" permission can hijack system namespaces label
IDs: CVE-2025-55205, GHSA-fcpm-6mxq-m5vv
Record: https://patchnext.com/advisories/cve-2025-55205 (revision 1, source checked 26 Oct 2026, 15:10 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/projectcapsule/capsule 0.10.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/projectcapsule/capsule: affected < 0.10.4; fixed in 0.10.4

## Suggested inspection (read-only)
- Go github.com/projectcapsule/capsule: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/projectcapsule/capsule.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-fcpm-6mxq-m5vv (GitHub-reviewed advisory GHSA-fcpm-6mxq-m5vv lists affected ranges: Go github.com/projectcapsule/capsule >=0 <0.10.4)

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