SSRF via Metalink Mirror URL Resolution:
An authenticated tenant can register a template pointing to an attacker-controlled metalink file containing internal targets. The Secondary Storage VM will retrieve the data and persist it as a template file, which can later be downloaded through normal APIs.
RCE on KVM hypervisor via NFS, Metalink files with/without Direct Downloads:
An authenticated CloudStack tenant holding the default User role can execute arbitrary shell commands as root on the KVM hypervisor host that runs other tenants' VMs. This is cross-tenant root on the underlying compute, reachable via the public CloudStack API.
When a User registers a VM template with directDownload=true and a URL pointing to a .metalink file, the management server fetches the metalink XML and dispatches download to the KVM agent. Inner URLs inside the metalink XML are never re-validated against the scheme allowlist.
These issues affect Apache CloudStack: from 4.14.0.0 through 4.20.3.0 and from 4.21.0.0 through 4.22.1.0.
Users are recommended to upgrade to version 4.20.3.1 or 4.22.1.1 or later, which fixes the issue.