A missing validation of Helm valuesFrom references in Rancher Fleet’s Helm Deployer permits a tenant owner with the ability to create or modify Helm releases to reference a secret stored in a different tenant’s namespace. Because the deployer fails to check that the referenced secret belongs to the same namespace or tenant, the requesting user can read protected credentials such as API keys or passwords that belong to another tenant. This weakness, identified as CWE‑1287 (Missing Access Control to Shared Resources), results in a confidentiality breach of secrets, and can enable further lateral movement within a multi‑tenant Rancher cluster.

The flaw affects all Rancher Fleet installations on versions 0.12.15 or earlier, 0.13.11 or earlier, 0.14.6 or earlier, and 0.15.2 or earlier. Any infrastructure that uses these releases and allows tenants to deploy or edit Helm charts is at risk. Systems running newer releases (0.12.16+, 0.13.12+, 0.14.7+, 0.15.3+) are not vulnerable.

The CVSS base score of 9.9 indicates a critical vulnerability. The EPSS score of < 1% suggests that large‑scale exploitation is currently unlikely, and the issue is not listed in CISA’s KEV catalog, but the nature of the vulnerability means that any tenant who can create or modify a Helm release could control a cross‑namespace valuesFrom reference and obtain sensitive secrets. The attack vector is internal to the cluster, requiring only Helm deployment rights, which many tenants are granted for workload management. Consequently, the risk remains high and patching should be performed immediately.