ToolHive is a utility designed to simplify the deployment and management of Model Context Protocol servers. Prior to ToolHive CLI 0.30.1 and ToolHive Studio 0.38.0, locally run MCP server containers use the default network permission profile without network isolation, permitting access to host.docker.internal while ToolHive API and MCP proxy endpoints are reachable without authentication. A malicious or compromised MCP server can use the Docker gateway to contact host-local services, other ToolHive-managed MCP proxies, or the ToolHive control plane without escaping the container. This access can expose data and logs, invoke sibling MCP tools, alter process or workload state, and disrupt services. ToolHive Studio additionally sends network_isolation as false and overrides the backend's secure isolation default. This issue is fixed in ToolHive CLI 0.30.1 and ToolHive Studio 0.38.0.

ToolHive is a utility designed to simplify the deployment and management of Model Context Protocol (MCP) servers. Prior to 0.31.0, remote.Handler.Authenticate in pkg/auth/remote/handler.go invokes discovery.DetectAuthenticationFromServer in pkg/auth/discovery/discovery.go, whose host-side HTTP clients trust remote-server-controlled authentication discovery destinations, follow redirects without host or scheme restrictions, and do not consistently block private addresses. A malicious or compromised remote MCP server can place a resource_metadata URL in WWW-Authenticate for ParseWWWAuthenticate to extract, after which FetchResourceMetadata, OIDC issuer discovery, and well-known discovery can issue GET requests to link-local, RFC1918, or other internal services outside the server's container. The user connects to a server that the user intends to use, but the server controls the internal destination; this path does not depend on the separate NAT64 guard omission because the affected clients did not invoke IsPrivateIP, and it differs from the DCR resolver path that already refused redirects. The demonstrated primitive reaches internal-only HTTP services and reachability or error oracles, and can retrieve AWS metadata credentials where IMDSv1 accepts an unauthenticated GET, while IMDSv2 and GCP metadata prerequisites are not satisfied by the demonstrated request. This vulnerability is fixed in 0.31.0.

ToolHive is a utility designed to simplify the deployment and management of Model Context Protocol (MCP) servers. Prior to 0.29.1, networking.IsPrivateIP in pkg/networking/utilities.go omits the IPv6 NAT64 prefixes 64:ff9b::/96 and 64:ff9b:1::/48, so NAT64 addresses embedding private, loopback, or link-local IPv4 targets are classified as public and allowed. The most direct attacker-controlled path begins when an external OAuth client supplies a client_id URL that CIMDStorageDecorator.GetClient routes through FetchClientMetadataDocument in pkg/oauthproto/cimd/fetch.go; protectedDialerControl in pkg/networking/http_client.go and validateHost in pkg/skills/gitresolver/reference.go share the defective classification but use operator-controlled or user-controlled destinations. On a ToolHive host behind a NAT64/DNS64 gateway, the gateway translates an allowed address such as 64:ff9b:1::a9fe:a9fe to 169.254.169.254, permitting blind probing of internal TCP or TLS reachability. The attacker-controlled CIMD path requires HTTPS, verifies certificates, and does not reflect response bodies, so the established impact is an internal reachability oracle rather than metadata credential exfiltration; the webhook client is not affected because it does not use this IP guard. This issue is fixed in version 0.29.1.