---
id: CVE-2026-109527
title: >-
  The Model Context Protocol Python SDK is the official Python SDK for Model
  Context Protocol servers and clients
summary: >-
  The Model Context Protocol Python SDK is the official Python SDK for Model
  Context Protocol servers and clients. In mcp versions before 1.29.1 and from
  2.0.0a1 through 2.0.1, the Streamable HTTP session manager, SSE message
  endpoint, and…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-770
published: '2026-10-14'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T18:17:33.447'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-109527'
references:
  - url: >-
      https://github.com/modelcontextprotocol/python-sdk/commit/03aaebd3aadb2567878dd811cb1f141454e8a080
    label: security-advisories@github.com
  - url: >-
      https://github.com/modelcontextprotocol/python-sdk/commit/4dc224fab201bdef2fd5a065976b7ca31420187c
    label: security-advisories@github.com
  - url: >-
      https://github.com/modelcontextprotocol/python-sdk/commit/57394b0548d1e2dc2dce8d67d84985769df3b8bb
    label: security-advisories@github.com
  - url: >-
      https://github.com/modelcontextprotocol/python-sdk/commit/5f0b6af9f2b0aad3be3ba5cbfe80a9e4ea32e189
    label: security-advisories@github.com
  - url: 'https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.29.1'
    label: security-advisories@github.com
  - url: 'https://github.com/modelcontextprotocol/python-sdk/releases/tag/v2.1.0'
    label: security-advisories@github.com
  - url: >-
      https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-fmmv-w9g8-j3gc
    label: security-advisories@github.com
tags:
  - nvd
ingestedAt: '2026-10-14T18:47:39.312Z'
---

## Overview

The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients. In mcp versions before 1.29.1 and from 2.0.0a1 through 2.0.1, the Streamable HTTP session manager, SSE message endpoint, and OAuth authorization-server routes buffer complete HTTP request bodies without enforcing a maximum size. An unauthenticated remote client able to reach an affected endpoint can send a large declared or streamed request body that consumes multiple times the body size in process memory and can repeatedly exhaust memory or terminate the server. Stdio-only servers and deployments with an effective upstream request-size limit are not affected, and applications that use StreamableHTTPServerTransport directly remain responsible for enforcing their own limit. The standard SDK server applications and session managers are fixed in versions 1.29.1 and 2.1.0.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.