modelcontextprotocol python-sdk up to 1.29.x/2.1.x Token Verifier improper authorization

Summaryinfo

A vulnerability, which was classified as critical, was found in modelcontextprotocol python-sdk up to 1.29.x/2.1.x. Affected by this vulnerability is an unknown functionality of the component Token Verifier. The manipulation results in improper authorization. This vulnerability was named CVE-2026-116684. The attack may be performed from remote. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, was found in modelcontextprotocol python-sdk up to 1.29.x/2.1.x. Affected is some unknown functionality of the component Token Verifier. The manipulation with an unknown input leads to a improper authorization vulnerability. CWE is classifying the issue as CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-116684 since 10/26/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1548.002.

Upgrading to version 1.30.0 or 2.2.0 eliminates this vulnerability.

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Productinfo

Type

• Programming Language Software

Vendor

• modelcontextprotocol

Name

• python-sdk

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19
• 1.20
• 1.21
• 1.22
• 1.23
• 1.24
• 1.25
• 1.26
• 1.27
• 1.28
• 1.29
• 2.0
• 2.1

Website

• Product: https://github.com/modelcontextprotocol/python-sdk/

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