Stacklok ToolHive up to 0.30.x Authentication Discovery handler.go remote.Handler.Authenticate redirect

Summaryinfo

A vulnerability categorized as problematic has been discovered in Stacklok ToolHive up to 0.30.x. The impacted element is the function remote.Handler.Authenticate of the file pkg/auth/remote/handler.go of the component Authentication Discovery. Executing a manipulation can lead to redirect. This vulnerability is handled as CVE-2026-58196. The attack can be executed remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Stacklok ToolHive up to 0.30.x and classified as problematic. This vulnerability affects the function remote.Handler.Authenticate of the file pkg/auth/remote/handler.go of the component Authentication Discovery. The manipulation with an unknown input leads to a redirect vulnerability. The CWE definition for the vulnerability is CWE-601. A web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a Redirect. This simplifies phishing attacks. As an impact it is known to affect integrity. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-58196 since 06/29/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1204.001.

Upgrading to version 0.31.0 eliminates this vulnerability.

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Productinfo

Vendor

• Stacklok

Name

• ToolHive

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7
• 0.8
• 0.9
• 0.10
• 0.11
• 0.12
• 0.13
• 0.14
• 0.15
• 0.16
• 0.17
• 0.18
• 0.19
• 0.20
• 0.21
• 0.22
• 0.23
• 0.24
• 0.25
• 0.26
• 0.27
• 0.28
• 0.29
• 0.30

Website

• Product: https://github.com/stacklok/toolhive/

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