Capsule: Incomplete fix of CVE-2026-30963: singular/plural typo leaves namespaces/finalize unprotected

Exploitation

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

CVSS

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

EPSS

• CVE-2026-55636: 0.39% estimated exploitation activity in the next 30 days; percentile 32.63 (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 Capsule v0.13.2 webhook rules contain namespace/finalize (singular) instead of namespaces/finalize (plural). K8s requires plural. The finalize defense from CVE-2026-30963 fix is absent. Details PUT to /api/v1/namespaces/<ns/finalize has resource=namespaces (plural). The singular rule never matches. matchPolicy: Equivalent does not compensate. PoC Confirmed on kind + Capsule v0.13.2. alice (non-admin with namespaces/finalize RBAC): kubectl label --as=alice = DENIED (control). kubectl replace --raw /finalize --as=alice = 200 OK (bypass). Tenant label changed. Impact Namespace tenant-label hijack. Same threat model as CVE-2026-30963. One-char fix: namespace/finalize - namespaces/finalize. The CVE-2026-30963 fix in Capsule v0.13.2 added subresource entries to the namespace validating webhook, but charts/capsule/templates/configuration.yaml line 105 contains a singular/plural typo: namespace/finalize instead of namespaces/finalize. Kubernetes webhook rules require the plural…

Published by the source

17 Jun 2026, 18:14 UTC

Last modified by the source

17 Jun 2026, 18:14 UTC

Source last checked

26 Oct 2026, 15:24 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-gwxr-7h77-7777

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# Patch Next advisory brief: CVE-2026-55636

Advisory: Capsule: Incomplete fix of CVE-2026-30963: singular/plural typo leaves namespaces/finalize unprotected
IDs: CVE-2026-55636, GHSA-gwxr-7h77-7777
Record: https://patchnext.com/advisories/cve-2026-55636 (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.7)
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 0.13.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/projectcapsule/capsule: affected >= 0.13.0, < 0.13.6; fixed in 0.13.6

## 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-gwxr-7h77-7777 (GitHub-reviewed advisory GHSA-gwxr-7h77-7777 lists affected ranges: Go github.com/projectcapsule/capsule >=0.13.0 <0.13.6)

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