---
title: "CVE-2026-109527: Model Context Protocol Python SDK - Denial of Service"
description: "Model Context Protocol Python SDK < 1.29.1 and 2.0.0a1 through 2.0.1 contain a denial of service caused by unbounded buffering of HTTP request bodies in Streamable HTTP session manager and related components, letting unauthenticated remote clients exhaust server memory, exploit requires network access to affected endpoints."
url: https://panop.io/threat-heartbeat/CVE-2026-109527/
---

# CVE-2026-109527 Model Context Protocol Python SDK - Denial of Service

Model Context Protocol Python SDK < 1.29.1 and 2.0.0a1 through 2.0.1 contain a denial of service caused by unbounded buffering of HTTP request bodies in Streamable HTTP session manager and related components, letting unauthenticated remote clients exhaust server memory, exploit requires network access to affected endpoints.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-109527)

## Details

Type

Denial of Service

Impact

Denial Of Service

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Published

14 October 2026

Updated

15 October 2026

Weakness

[CWE-770](https://cwe.mitre.org/data/definitions/770.html)

## Vendor fix

Upgrade to versions 1.29.1 or 2.1.0 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-109527](https://nvd.nist.gov/vuln/detail/CVE-2026-109527)
- [https://github.com/modelcontextprotocol/python-sdk/commit/4dc224fab201bdef2fd5a065976b7ca31420187c](https://github.com/modelcontextprotocol/python-sdk/commit/4dc224fab201bdef2fd5a065976b7ca31420187c)
- [https://github.com/modelcontextprotocol/python-sdk/commit/57394b0548d1e2dc2dce8d67d84985769df3b8bb](https://github.com/modelcontextprotocol/python-sdk/commit/57394b0548d1e2dc2dce8d67d84985769df3b8bb)
- [https://github.com/modelcontextprotocol/python-sdk/commit/5f0b6af9f2b0aad3be3ba5cbfe80a9e4ea32e189](https://github.com/modelcontextprotocol/python-sdk/commit/5f0b6af9f2b0aad3be3ba5cbfe80a9e4ea32e189)
- [https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.29.1](https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.29.1)
- [https://github.com/modelcontextprotocol/python-sdk/releases/tag/v2.1.0](https://github.com/modelcontextprotocol/python-sdk/releases/tag/v2.1.0)
- [https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-fmmv-w9g8-j3gc](https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-fmmv-w9g8-j3gc)
- [https://github.com/modelcontextprotocol/python-sdk/commit/03aaebd3aadb2567878dd811cb1f141454e8a080](https://github.com/modelcontextprotocol/python-sdk/commit/03aaebd3aadb2567878dd811cb1f141454e8a080)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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