MCPHub is a unified hub for centrally managing and dynamically orchestrating multiple MCP servers/APIs into separate endpoints with flexible routing strategies. Prior to version 1.0.31, when a bearer key with accessType: 'servers' (or 'custom') is used against a group route, isBearerKeyAllowedForRequest grants access to the entire group as long as any single server in that group appears in the key's allowedServers list — not only when every server the key is scoped to matches, and critically, without ever re-checking allowedServers again once the group-level connection is authorized. A key explicitly scoped to one specific server therefore also grants full access to every other server that happens to share a group with it, including servers the key was never authorized for. This issue has been patched in version 1.0.31.

MCPHub, a unified hub for managing and orchestrating multiple MCP servers/APIs, contains an authorization bypass vulnerability prior to version 1.0.31. The flaw exists in the isBearerKeyAllowedForRequest function, which incorrectly grants access to an entire server group when a bearer key with accessType 'servers' or 'custom' is used against a group route. Access is granted if any single server in the group appears in the key's allowedServers list, rather than verifying all servers. Once group-level access is authorized, allowedServers is never re-checked. This means a key scoped to one specific server inadvertently grants full access to all other servers sharing the same group, including those the key was never authorized for. The vulnerability represents a significant privilege escalation risk in multi-server environments. The issue has been fully patched in MCPHub version 1.0.31.