ToolHive: SSRF in remote MCP server authentication discovery (host-side, bypasses container isolation) (CVE-2026-58196) | HOL Guard CVE

Low severityCVE-2026-58196GHSA-PR64-JMMF-JP54

ToolHive: SSRF in remote MCP server authentication discovery (host-side, bypasses container isolation)

Answer in brief

CVE-2026-58196 records a Low severity vulnerability in ToolHive: SSRF in remote MCP server authentication discovery (host-side, bypasses container isolation). The current sources do not mark it as known exploited. The current feed maps stacklok/toolhive (generic), github.com/stacklok/toolhive (go). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 15, 2026Updated Sep 15, 2026Source checked Sep 17, 2026First seen by HOL Jul 16, 2026Material review Sep 15, 2026

Upstream Advisory

Key facts

Risk: Low
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps stacklok/toolhive (generic), github.com/stacklok/toolhive (go). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
stacklok/toolhivegeneric	< 0.31.0	Not reported
github.com/stacklok/toolhivego	<0.31.0	0.31.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for stacklok/toolhive, github.com/stacklok/toolhive.
Review the reported fix. Update github.com/stacklok/toolhive to 0.31.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 15, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 15, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Jul 16, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.