The vulnerability resides in how Capsule’s ForbiddenListSpec.ExactMatch sorts denied metadata keys. The implementation sorts keys case‑insensitively but then performs a byte‑order binary search. When a forbidden list mixes capitalized and lowercase keys, the two orderings diverge, causing the search to miss valid entries. An authenticated tenant owner can exploit this by including a mis‑ordered key that the system mistakenly treats as allowed, thereby passing through api.ValidateForbidden and bypassing configured namespace, Service, or node metadata restrictions. This gives the tenant owner the ability to influence cluster policies, network exposure, or scheduling beyond the intended tenant boundary, effectively escalating privileges within the cluster. The weakness is encapsulated by CWE‑697 and CWE‑863, indicating reliance on erroneous conditions for safety checking and improper input validation in a security control. The CVSS score of 7.1 indicates a high severity.

The affected product is Capsule, the multi‑tenancy framework for Kubernetes developed by Project Capsule. Versions prior to 0.13.7 are vulnerable, as the patch that corrects the sorting and binary search logic is released with the 0.13.7 release. Current installations using any earlier revision must be considered at risk until they apply the fix.

The exploit requires the ability to own or create a tenant, granting authentication as a tenant owner. Once authenticated, the attacker crafts a forbidden list entry that the system mis‑interprets, delegating permission to bypass namespace, Service, or node restrictions. The vulnerability is not dependent on network exposure or privileged system access; it can be executed from anywhere a tenant owner can configure settings. The EPSS score is not available, but the CVSS 7.1 rating implies significant potential impact. The vulnerability is not listed in CISA’s KEV catalog, suggesting no known widespread exploitation yet, but the attack vector remains viable in any open‑cluster environment where tenant owners have permission to alter forbidden lists. Prompt remediation is therefore advised to prevent privilege escalation.