CVE-2026-111771

What it is

The Model Context Protocol TypeScript SDK provides TypeScript client and server implementations of the Model Context Protocol. From 1.6.0 until 1.32.0 in @modelcontextprotocol/sdk, from 2.0.0 until 2.3.0 in @modelcontextprotocol/server, from 2.0.0 until 2.0.2 in @modelcontextprotocol/express, and from 2.0.0 until 2.3.1 in @modelcontextprotocol/server-legacy, server-side bearer authentication could accept a valid access token issued for a different service because the SDK did not enforce the token audience. The affected surface is server-side HTTP bearer authentication. The trigger is a valid token whose audience names another service. The authorization server must issue tokens for multiple services, and the application's verifyAccessToken() must not independently validate aud. Applications already validating aud inside verifyAccessToken() are not affected. An attacker with a token for another service could authenticate to the MCP server and obtain the confidentiality and integrity capabilities granted to an authenticated caller. Upgrading alone leaves the new audience validation disabled. Operators must enable audience validation and provide the token audience together. Enabling only the expected audience check causes every request to receive HTTP 401. This issue is fixed in @modelcontextprotocol/sdk 1.32.0, @modelcontextprotocol/server 2.3.0, @modelcontextprotocol/express 2.0.2, and @modelcontextprotocol/server-legacy 2.3.1.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of data exposure, data tampering.

Exploit odds

0.5% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-10-16 17:52 UTC ReservedThe CVE id was reserved by its CNA
2. 2026-11-05 21:18 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-11-10 05:17 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.5% in the next 30 days (EPSS).
• Severity: 6.8 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-11-05 21:18 UTC

Last modified

2026-11-10 05:17 UTC

Exploit probability

0.5% · EPSS, next 30 days

Weakness

CWE-863 · Incorrect authorization

Record status

Received

Attack profile CVSS 3.1 · 6.8

Attack vector

Network

Complexity

High

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-111771.md and follow it. Check whether this project is affected by CVE-2026-111771. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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