Server-side request forgery (SSRF) in Istio's Wasm OCI image fetcher. The validateRealmURL function in pkg/wasm/imagefetcher.go validates the WWW-Authenticate bearer realm returned by an OCI registry using net.ParseIP, which returns nil for hostnames, so IP-range blocking is skipped for any non-IP host. A malicious registry can set the realm to internal DNS names (e.g. kubernetes.default.svc, metadata.azure.com), the unspecified address (0.0.0.0, [::], routed to loopback on Linux), or trailing-dot FQDN forms of blocked hosts (localhost., 127.0.0.1., metadata.google.internal.) to make istiod send requests to the Kubernetes API server, in-cluster services, and cloud metadata endpoints.