CVE-2026-72920: SeaweedFS: Unauthenticated filer IAM gRPC service grants S3 administrative control

The filer registered the IAM gRPC service (SeaweedIdentityAccessManagement) with no authentication. Any client able to reach the filer gRPC port could invoke IAM RPCs — CreateUser, CreateAccessKey, PutUserPolicy, and related calls — to mint credentials and grant itself S3 administrative privileges. This fully compromises the confidentiality, integrity, and availability of stored objects.

No credentials are required, and enabling the documented JWT signing keys does not close it: the IAM gRPC service was not gated by that mechanism. Even under mTLS, the listener-level allowed_commonNames ACL applies to the port rather than to individual RPCs, so any cluster mesh certificate could reach these administrative calls.