CVE-2026-109527

waiting for further signals

GHSA-fmmv-w9g8-j3gc ↗EUVD-2026-101514 ↗

no check availablenot proven exploitable

cve.orgpublic pockev

pip:mcp < 1.29.1; >= 2.0.0, < 2.1.0

fixed in 1.29.1, 2.1.0

CWE-770 Allocation of Resources Without Limits or Throttling

ETK-2026-154, permanent identifier

pkg:pypi/mcp

cvss7.5cna vendorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

6d 14h 45msince last run

26mAI analysis

timeline

0 = cve.org publication

trigger signal −14dcve.org publicationwaiting for further signals+0.1d

−10d

−5d

description

The Python mcp SDK is affected when an HTTP server uses versions before 1.29.1 in the 1.x line or 2.0.0 through 2.0.1. An unauthenticated client that can reach affected HTTP, SSE, or OAuth routes can cause excessive memory consumption and disrupt the server by submitting an oversized request. Stdio-only servers and deployments with an effective upstream request-body limit are not affected.

mitigation

Upgrade mcp to 1.29.1 or later on the 1.x line, or 2.1.0 or later on the 2.x line. Until upgraded, enforce request-body size limits in a reverse proxy or ASGI middleware; directly used StreamableHTTPServerTransport instances must apply their own limit.

fixed in 1.29.1, 2.1.0

check

exploit

automation

–

auth required

EPSS

0.70%52nd percentile

agent run time

26m

cve.org record, t = 0

2026-10-14 17:52Z

Δ to public poc

–

Δ to kev

–

outcome

No artifact: an exploit or check was attempted but could not be produced at this moment.

source signals

Public signals that triggered or updated the pipeline. These are inputs for the deltas above.

2026-09-30 20:53Z
ghsa: trigger signal, started the run
https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-fmmv-w9g8-j3gc
2026-10-14 17:52Z
cve.org record for CVE-2026-109527
cve_org · https://www.cve.org/CVERecord?id=CVE-2026-109527

this entry in the feed

GET /api/v1/feed/CVE-2026-109527

{
  "etk_id": "ETK-2026-154",
  "cve_id": "CVE-2026-109527",
  "display_id": "CVE-2026-109527",
  "ghsa_id": "GHSA-fmmv-w9g8-j3gc",
  "euvd_id": "EUVD-2026-101514",
  "status": "published",
  "anchor_state": "anchored",
  "title": "Unbounded HTTP request-body buffering in mcp",
  "summary": "The Python `mcp` SDK is affected when an HTTP server uses versions before 1.29.1 in the 1.x line or 2.0.0 through 2.0.1. An unauthenticated client that can reach affected HTTP, SSE, or OAuth routes can cause excessive memory consumption and disrupt the server by submitting an oversized request. Stdio-only servers and deployments with an effective upstream request-body limit are not affected.",
  "mitigation": "Upgrade `mcp` to 1.29.1 or later on the 1.x line, or 2.1.0 or later on the 2.x line. Until upgraded, enforce request-body size limits in a reverse proxy or ASGI middleware; directly used `StreamableHTTPServerTransport` instances must apply their own limit.",
  "vendor": "pip",
  "product": "pip:mcp",
  "affected": [
    {
      "affected_notes": [],
      "affected_ranges": [
        "< 1.29.1"
      ],
      "ecosystem": "pip",
      "fixed_versions": [
        "1.29.1"
      ],
      "package_name": "mcp",
      "purl": "pkg:pypi/mcp"
    },
    {
      "affected_notes": [],
      "affected_ranges": [
        ">= 2.0.0, < 2.1.0"
      ],
      "ecosystem": "pip",
      "fixed_versions": [
        "2.1.0"
      ],
      "package_name": "mcp",
      "purl": "pkg:pypi/mcp"
    }
  ],
  "cwes": [
    770
  ],
  "cvss_score": 7.5,
  "cvss_src": "cna_vendor",
  "cvss_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
  "epss_score": 0.007,
  "epss_percentile": 0.5235,
  "epss_asof": "2026-10-20",
  "automation": "deterministic",
  "check": false,
  "check_confidence_basis": null,
  "exploit": false,
  "pipeline_minutes": 26.19307225,
  "t0_at": "2026-10-14T17:52:35.943000+00:00",
  "signals": {
    "trigger_signal": {
      "at": "2026-09-30T20:53:39+00:00",
      "days": -13.87427017361111,
      "is_lower_bound": false,
      "measured_at": "2026-10-14T17:52:35.943000+00:00",
      "url": "https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-fmmv-w9g8-j3gc"
    }
  }
}

Anchor corroborated by the cve.org commit cf6d4d725208.

published 2026-09-30 21:14Z
last change 2026-10-21 09:11Z

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