Description
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.
References7
- github.com/modelcontextprotocol/python-sdk/commit/0c9136841ff09…
- github.com/modelcontextprotocol/python-sdk/commit/8c2fa6eabacde…
- github.com/modelcontextprotocol/python-sdk/pull/3447
- github.com/modelcontextprotocol/python-sdk/pull/3451
- github.com/modelcontextprotocol/python-sdk/releases/tag/v1.30.0
- github.com/modelcontextprotocol/python-sdk/releases/tag/v2.2.0
- github.com/modelcontextprotocol/python-sdk/security/advisories/…
Metrics
- CVSS 3.1
-
6.8
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N - EPSS — exploit probability
- 0% percentile: 31 · as of 4 November 2026
- CWE
- CWE-863
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.