Remote Authentication Bypass in ToolHive by Stacklok

CVE-2026-58196

What is CVE-2026-58196?

ToolHive, a utility for managing Model Context Protocol (MCP) servers, has a vulnerability where remote authentication mechanisms are not securely configured prior to version 0.31.0. The application trusts remote-server-controlled authentication discovery destinations, which enables a malicious remote MCP server to manipulate authentication URLs and potentially access internal services. Specifically, the flawed authentication process can lead to unauthorized access to link-local or private network services, such as retrieving sensitive AWS metadata credentials, through improper host and scheme handling. This critical security issue has been addressed in the updated version 0.31.0.

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