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[ CVE-2026-116684 · Published 27 Oct 2026 ]

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

CVSS 6.8 EPSS <1%Fix available

[ Description ]Official 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.

[ Fixes ]Fixes and patches

  • mcp 2.2.0Fixed version · GitHub Advisories · pip package mcp: upgrade to 2.2.0 or later (affected >= 2.0.0, < 2.2.0)
  • mcp 1.30.0Fixed version · GitHub Advisories · pip package mcp: upgrade to 1.30.0 or later (affected >= 1.10.0, < 1.30.0)

[ Packages ]Affected open-source packages

[ References ]References