CVE-2026-116684

MEDIUM 6.8

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

CVSS Score

6.8

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-863
Vendor	modelcontextprotocol
Product	python-sdk
Published	Oct 27, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

Attack Vector

Network

Attack Complexity

High

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Affected Versions

modelcontextprotocol / python-sdk

>= 1.10.0, < 1.30.0 >= 2.0.0, < 2.2.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-w4fh-qvv9-3v23 github.com: https://github.com/modelcontextprotocol/python-sdk/pull/3447 github.com: https://github.com/modelcontextprotocol/python-sdk/pull/3451 github.com: https://github.com/modelcontextprotocol/python-sdk/commit/0c9136841ff092987a20700ff9c2c9789bda2f40 github.com: https://github.com/modelcontextprotocol/python-sdk/commit/8c2fa6eabacde869d75568e33b9d466b58c2f512 github.com: https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.30.0 github.com: https://github.com/modelcontextprotocol/python-sdk/releases/tag/v2.2.0