---
id: CVE-2026-108859
title: >-
  mcp-go through 1.2.1 contains a denial of service vulnerability in
  StreamableHTTPServer.ServeHTTP that allows remote unauthenticated attackers to
  exhaust memory by sending oversized POST bodies
summary: >-
  mcp-go through 1.2.1 contains a denial of service vulnerability in
  StreamableHTTPServer.ServeHTTP that allows remote unauthenticated attackers to
  exhaust memory by sending oversized POST bodies. Attackers can send
  arbitrarily large or ma…
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: '2026-10-11'
updated: '2026-10-11'
sourceUpdated: '2026-10-11T14:17:05.893'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-108859'
references:
  - url: 'https://github.com/mark3labs/mcp-go'
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/mark3labs/mcp-go/blob/90d247ed8d45cbb7d71d9a95e112789b78760443/server/streamable_http.go#L405-L411
    label: disclosure@vulncheck.com
  - url: >-
      https://hackmd.io/@1ExmmukzRMWN7B4gQ4W-4Q/mark3labs-mcp-go-streamable-http-unbounded-body
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/mcp-go-through-1.2.1-denial-of-service-via-unbounded-post-body-buffering
    label: disclosure@vulncheck.com
tags:
  - nvd
ingestedAt: '2026-10-12T14:50:34.052Z'
---

## Overview

mcp-go through 1.2.1 contains a denial of service vulnerability in StreamableHTTPServer.ServeHTTP that allows remote unauthenticated attackers to exhaust memory by sending oversized POST bodies. Attackers can send arbitrarily large or many concurrent POST requests, read fully via io.ReadAll before validation, to degrade or OOM-kill the server process.

## Remediation

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