CVE-2026-109527 (GCVE-0-2026-109527)

Vulnerability from cvelistv5 – Published: 2026-10-14 17:52 – Updated: 2026-10-14 17:52
VLAI
Title
Model Context Protocol Python SDK HTTP and OAuth endpoints allow memory exhaustion through unbounded request bodies
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 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.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE
  • CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7637 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
modelcontextprotocol python-sdk Affected: < 1.29.1
Affected: >= 2.0.0a1, < 2.1.0
guessed Create a notification for this product.
Show details on NVD website
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        "discovery": "UNKNOWN"
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      "title": "Model Context Protocol Python SDK HTTP and OAuth endpoints allow memory exhaustion through unbounded request bodies"
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  "cveMetadata": {
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    "cveId": "CVE-2026-109527",
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    "dateReserved": "2026-10-12T19:11:21.789Z",
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          }
        ],
        "id": "CVE-2026-109527",
        "lastModified": "2026-10-14T18:17:33.447",
        "metrics": {
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      "current_release_date": "2026-10-15T10:52:25+00:00",
      "cve": "CVE-2026-109527",
      "id": "CVE-2026-109527",
      "initial_release_date": "2026-10-14T17:52:35.943000+00:00",
      "product_status:known_affected": "46",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "mcp: mcp: Denial of Service via unbounded HTTP request body buffering",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-109527.json",
      "version": "3"
    }
  }
}



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