CVE-2021-36783: Rancher doesn't properly sanitize credentials in cluster template answers

It was discovered that in Rancher versions up to and including 2.5.12 and 2.6.3 there is a failure to properly sanitize credentials in cluster template answers. This failure can lead to plaintext storage and exposure of credentials, passwords and API tokens.

The exposed credentials are visible in Rancher to authenticated Cluster Owners, Cluster Members, Project Owners and Project Members on the endpoints /v1/management.cattle.io.clusters, /v3/clusters and /k8s/clusters/local/apis/management.cattle.io/v3/clusters.

Sensitive fields are now stripped from Clusters objects before the object is stored. For objects that existed before this security fix, a one-time migration happens on startup.

Important:

• It is highly advised to review for potential leaked credentials in this scenario, and to change them if deemed necessary.
• The final impact severity for confidentiality, integrity and availability is dependent on the permissions that the leaked credentials have on their own services.