fkie_cve-2026-116684

The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients. From 1.10.0 until 1.30.0 and 2.2.0, server-side bearer authentication configured through AuthSettings with token_verifier accepts a valid token issued for another service when the authorization server serves multiple resources and the TokenVerifier does not independently validate the aud audience. This resource-confusion flaw lets a token holder authenticate to the wrong MCP server and exercise that token's resulting access. This issue is fixed in versions 1.30.0 and 2.2.0.

GHSA-w4fh-qvv9-3v23 — Model Context Protocol Python SDK: Server bearer-token authentication accepts tokens issued for a different resource se…

Affected: PyPI: mcp

### Summary In affected versions, the SDK's server-side bearer authentication had no way to check that a token was issued for your server (its audience). Where one authorization server issues tokens for several services, a valid token for another service was also accepted by your MCP server.

### Am I affected? Yes, if your HTTP server uses the SDK's bearer authentication (`auth=AuthSettings(...)` with `token_verifier=`), its authorization server also issues tokens for other services, and your `TokenVerifier` does not check the token's audience (`aud`) itself.

Affected versions:

- `mcp` 1.10.0 through 1.29.1 - `mcp` 2.0.0 through 2.1.1

### Fix Upgrade to:

- 1.x: `mcp` 1.30.0 or later - 2.x: `mcp` 2.2.0 or later

**Upgrading alone changes nothing.** The patched versions add a `validate_token_resource` setting that is off unless you set it. To turn the check on, make both of these changes together:

1. Set `validate_token_resource=True` in `AuthSettings`, with `resource_server_url` set to the audience your authorization server puts in tokens for your server. 2. Return the token's audience from `verify_token()` as `AccessToken.resource`.

A token for another service then gets `401`. With only the first change, every request gets `401`.

If your `TokenVerifier` already checks the audience, set `validate_token_resource=False` to silence the deprecation warning. The setting will default to `True` in 3.0.

If you cannot upgrade yet, reject any token whose `aud` does not include…

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fkie_cve-2026-116684

GHSA-w4fh-qvv9-3v23 — Model Context Protocol Python SDK: Server bearer-token authentication accepts tokens issued for a different resource se…