MCP TypeScript SDK server-side bearer authentication accepts tokens issued for other services
MCP TypeScript SDK: Server bearer authentication accepted tokens issued for another service
The MCP TypeScript SDK's server-side bearer authentication does not validate the token's audience in affected versions, so valid tokens issued by the authorization server for other services are also accepted by the MCP server. Affected versions include versions before @modelcontextprotocol/sdk 1.32.0, before @modelcontextprotocol/server 2.3.0, before @modelcontextprotocol/express 2.0.2, and before @modelcontextprotocol/server-legacy 2.3.1. If upgrading is not possible, tokens whose aud does not contain this service can be rejected in verifyAccessToken().
Teams building HTTP services with the MCP TypeScript SDK can use this to check token audience validation and enable the check with the two-step configuration given in the advisory.