Capsule: Tenant owner bypasses Capsule's forbidden namespace/service/node label and annotation enforcement

Capsule is a multi-tenancy and policy-based framework for Kubernetes. Prior to 0.13.7, ForbiddenListSpec.ExactMatch in pkg/api/forbidden_list.go sorts denied metadata keys case-insensitively and then uses sort.SearchStrings, which assumes byte-order sorting. When an administrator's forbidden list mixes capitalized and lowercase keys or otherwise has different case-insensitive and byte ordering, the binary search can return false for a key that is present. An authenticated tenant owner can then pass the missed key through api.ValidateForbidden and bypass configured namespace, Service, or delegated node metadata restrictions, potentially influencing cluster policies, network exposure, or scheduling outside the tenant boundary. Uniformly lowercase lists whose two orderings coincide are not affected. This issue is fixed in version 0.13.7.

Source published

18 Sep 2026 16:29:23 UTC

Source modified

22 Sep 2026 14:57:51 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 3.1 · 7.1 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:H/A:N