---
id: CVE-2026-111768
aliases:
  - GHSA-46jr-4wx8-v453
title: >-
  MCP TypeScript SDK: One HTTP request within the default size limit could
  exhaust server memory during validation
summary: >-
  MCP TypeScript SDK: One HTTP request within the default size limit could
  exhaust server memory during validation
severity: high
cvss: 7.5
cwe:
  - CWE-770
vendor: modelcontextprotocol
product: '@modelcontextprotocol/sdk'
ecosystem: npm
affected:
  - '@modelcontextprotocol/sdk >= 1.3.0, < 1.32.0'
  - '@modelcontextprotocol/server >= 2.0.0, < 2.3.0'
patched:
  - '@modelcontextprotocol/sdk 1.32.0'
  - '@modelcontextprotocol/server 2.3.0'
published: '2026-10-20'
updated: '2026-10-20'
sourceUpdated: '2026-10-20T20:06:38Z'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-46jr-4wx8-v453'
references:
  - url: >-
      https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-46jr-4wx8-v453
  - url: 'https://github.com/modelcontextprotocol/typescript-sdk/pull/2926'
  - url: 'https://github.com/modelcontextprotocol/typescript-sdk/pull/2927'
  - url: >-
      https://github.com/modelcontextprotocol/typescript-sdk/commit/6d8dbc6cb590edf766fcb66b636ca6b654e99c37
  - url: >-
      https://github.com/modelcontextprotocol/typescript-sdk/commit/fd26801b3b387742fe24a90ed4b275dd6072209f
  - url: 'https://github.com/advisories/GHSA-46jr-4wx8-v453'
tags:
  - ghsa
  - npm
ingestedAt: '2026-10-20T20:18:14.522Z'
---

## Overview

### Summary
In affected versions, servers put no limit on how many array elements and object keys they validated in one request. One HTTP request within the default 4 MiB size limit could exhaust the server's memory, and the process aborted with `JavaScript heap out of memory`.

No credentials are needed, unless you authenticate requests before they reach the SDK.

### Am I affected?
Yes, if clients you do not fully trust can reach your server over HTTP. The risk is highest for `McpServer` tools whose input contains an array or a record. stdio-only servers are not affected.

Affected versions:

- `@modelcontextprotocol/sdk` 1.3.0 through 1.31.0
- `@modelcontextprotocol/server` 2.0.0 through 2.2.0

### Fix
Upgrade to:

- 1.x: `@modelcontextprotocol/sdk` 1.32.0 or later
- 2.x: `@modelcontextprotocol/server` 2.3.0 or later

**Upgrading alone changes nothing.** The patched versions add an `McpServer` option, `maxToolInputElements`, that is off by default. Make both of these changes:

1. Set `maxToolInputElements` just above the largest input your tools need, for example `new McpServer(info, { maxToolInputElements: 10_000 })`. It counts array elements and object keys in a call's arguments. A call over the limit gets an `isError: true` result.
2. Lower the request size limit to what your tools need. The option covers tool arguments only, and the size limit covers everything else. Set `maxRequestBodySize` on the transport or `createMcpHandler()`. If you parse the body yourself, for example with `express.json()` or Fastify, set that parser's limit.

If you cannot upgrade yet, make the second change. `maxRequestBodySize` needs `@modelcontextprotocol/sdk` 1.30.1 or `@modelcontextprotocol/server` 2.1.0. Below that, use a reverse proxy.

## Affected packages

- `@modelcontextprotocol/sdk >= 1.3.0, < 1.32.0`
- `@modelcontextprotocol/server >= 2.0.0, < 2.3.0`

## Remediation

Upgrade to a patched release:

- `@modelcontextprotocol/sdk 1.32.0`
- `@modelcontextprotocol/server 2.3.0`