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Vulnerability · Published Oct 27, 2026 · Assigned by GitHub_M

CVE-2026-116684Model Context Protocol Python SDK: Server bearer-token authentication accepts tokens issued for a different resource server

Medium 6.8

In plain English

A medium-severity incorrect authorization in python-sdk from modelcontextprotocol. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 31% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.8Medium
Exploit odds (30 days)0.4%top 69.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
PyPImcp2.2.0GHSA-w4fh-qvv9-3v23
PyPImcp1.30.0GHSA-w4fh-qvv9-3v23

Affected products (as reported)

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

Weakness: CWE-863 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

References