---
id: CVE-2026-111771
aliases:
  - GHSA-rvq5-wwqv-78pq
title: >-
  MCP TypeScript SDK: Server bearer authentication accepted tokens issued for
  another service
summary: >-
  MCP TypeScript SDK: Server bearer authentication accepted tokens issued for
  another service
severity: medium
cvss: 6.8
cwe:
  - CWE-863
vendor: modelcontextprotocol
product: '@modelcontextprotocol/sdk'
ecosystem: npm
affected:
  - '@modelcontextprotocol/sdk >= 1.6.0, < 1.32.0'
  - '@modelcontextprotocol/server >= 2.0.0, < 2.3.0'
  - '@modelcontextprotocol/express >= 2.0.0, < 2.0.2'
  - '@modelcontextprotocol/server-legacy >= 2.0.0, < 2.3.1'
patched:
  - '@modelcontextprotocol/sdk 1.32.0'
  - '@modelcontextprotocol/server 2.3.0'
  - '@modelcontextprotocol/express 2.0.2'
  - '@modelcontextprotocol/server-legacy 2.3.1'
published: '2026-10-20'
updated: '2026-10-20'
sourceUpdated: '2026-10-20T19:43:37Z'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-rvq5-wwqv-78pq'
references:
  - url: >-
      https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-rvq5-wwqv-78pq
  - url: >-
      https://github.com/modelcontextprotocol/typescript-sdk/commit/40f8f4e229d963cd7fd2890bda2aeebe7005299a
  - url: >-
      https://github.com/modelcontextprotocol/typescript-sdk/commit/5a0724d14cf34a27a3b070224d2996cdd611df9f
  - url: >-
      https://github.com/modelcontextprotocol/typescript-sdk/commit/5a1867390b91b8836f49af76c45427279f513325
  - url: 'https://github.com/advisories/GHSA-rvq5-wwqv-78pq'
tags:
  - ghsa
  - npm
ingestedAt: '2026-10-20T20:18:14.524Z'
---

## Overview

### Summary
In affected versions, the SDK's server-side bearer authentication had no way to check that a token was issued for your server (its audience). Where one authorization server issues tokens for several services, a valid token for another service was also accepted by your MCP server.

### Am I affected?
Yes, if your HTTP server uses `requireBearerAuth()` or `verifyBearerToken()`, its authorization server also issues tokens for other services, and your `verifyAccessToken()` does not check the token's audience (`aud`) itself.

Affected versions:

- `@modelcontextprotocol/sdk` 1.6.0 through 1.31.0
- `@modelcontextprotocol/server` 2.0.0 through 2.2.0
- `@modelcontextprotocol/express` 2.0.0 through 2.0.1
- `@modelcontextprotocol/server-legacy` 2.0.0 through 2.3.0

### Fix
Upgrade to:

- 1.x: `@modelcontextprotocol/sdk` 1.32.0 or later
- 2.x: `@modelcontextprotocol/server` 2.3.0 or later, together with `@modelcontextprotocol/express` 2.0.2 or later if you use it
- `@modelcontextprotocol/server-legacy` 2.3.1 or later

**Upgrading alone changes nothing.** The patched versions add an `expectedResource` setting that is off by default. To turn the check on, make both of these changes together:

1. Pass the audience your authorization server puts in tokens for your server: `requireBearerAuth({ verifier, expectedResource: new URL('https://mcp.example.com/mcp') })`.
2. Return the token's audience from `verifyAccessToken()` as `AuthInfo.resource`, also a `URL`.

A token for another service then gets `401`. With only the first change, every request gets `401`.

If you cannot upgrade yet, reject any token whose `aud` does not include your server inside `verifyAccessToken()`. That closes the issue on every version.

## Affected packages

- `@modelcontextprotocol/sdk >= 1.6.0, < 1.32.0`
- `@modelcontextprotocol/server >= 2.0.0, < 2.3.0`
- `@modelcontextprotocol/express >= 2.0.0, < 2.0.2`
- `@modelcontextprotocol/server-legacy >= 2.0.0, < 2.3.1`

## Remediation

Upgrade to a patched release:

- `@modelcontextprotocol/sdk 1.32.0`
- `@modelcontextprotocol/server 2.3.0`
- `@modelcontextprotocol/express 2.0.2`
- `@modelcontextprotocol/server-legacy 2.3.1`