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OpenAdvisories
Medium · 6.8 CVE-2026-116684 EUVD-2026-111369GHSA-w4fh-qvv9-3v23

Model Context Protocol Python SDK: Server bearer-token authentication accepts tokens issued for a different resource server

Published Oct 27, 2026 · Updated Nov 2, 2026 · Assigned by GitHub_M

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.

Affected products

VendorProductAffectedFixed
modelcontextprotocol python-sdk >= 1.10.0, < 1.30.0, >= 2.0.0, < 2.2.0 —

Affected packages

EcosystemPackageAffectedFixedRecord
PyPI mcp >= 2.0.0, < 2.2.0 2.2.0 GHSA-w4fh-qvv9-3v23
PyPI mcp >= 1.10.0, < 1.30.0 1.30.0 GHSA-w4fh-qvv9-3v23

References