ToolHive: SSRF in remote MCP server authentication discovery (host-side, bypasses container isolation)
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
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| stacklok | toolhive | affected |
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| Stacklok | Toolhive |
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| Source | ID | Title |
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Github GHSA |
GHSA-pr64-jmmf-jp54 | ToolHive: SSRF in remote MCP server authentication discovery (host-side, bypasses container isolation) |
No CVSS v4.0
No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
Exploit prediction score: < 1% (0.429% probability within 30 days)
| Type | Values Removed | Values Added |
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| First Time appeared |
Stacklok
Stacklok toolhive |
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| Vendors & Products |
Stacklok
Stacklok toolhive |
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| Metrics |
ssvc
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| Description | 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. | |
| Title | ToolHive: SSRF in remote MCP server authentication discovery (host-side, bypasses container isolation) | |
| Weaknesses | CWE-918 | |
| References |
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| Metrics |
cvssV3_1
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