CVE-2026-59951

{
  "etk_id": "ETK-2026-155",
  "cve_id": "CVE-2026-59951",
  "display_id": "CVE-2026-59951",
  "ghsa_id": "GHSA-84m7-p3x7-pcfv",
  "euvd_id": "EUVD-2026-101452",
  "status": "published",
  "anchor_state": "anchored",
  "title": "Unbounded session retention in mcp Streamable HTTP servers",
  "summary": "Stateful Streamable HTTP servers in affected `mcp` releases retain session state without effective expiry or a session-count bound. A client able to reach the endpoint can cause unbounded memory growth by opening sessions; authentication does not prevent this for authenticated clients with access.",
  "mitigation": "Upgrade `mcp` to 1.30.0 or later on the 1.x line, or 2.2.0 or later on the 2.x line. If upgrading is not immediately possible, use `stateless_http=True` where session state is unnecessary, or restrict endpoint access.",
  "vendor": "pip",
  "product": "pip:mcp",
  "affected": [
    {
      "affected_notes": [],
      "affected_ranges": [
        ">= 1.8.0, < 1.30.0"
      ],
      "ecosystem": "pip",
      "fixed_versions": [
        "1.30.0"
      ],
      "package_name": "mcp",
      "purl": "pkg:pypi/mcp"
    },
    {
      "affected_notes": [],
      "affected_ranges": [
        ">= 2.0.0, < 2.2.0"
      ],
      "ecosystem": "pip",
      "fixed_versions": [
        "2.2.0"
      ],
      "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": 0.0046,
  "epss_percentile": 0.3838,
  "epss_asof": "2026-10-20",
  "automation": "contextual",
  "check": false,
  "check_confidence_basis": null,
  "exploit": false,
  "pipeline_minutes": 11.595502116666667,
  "t0_at": "2026-10-14T16:22:31.653000+00:00",
  "signals": {
    "trigger_signal": {
      "at": "2026-09-30T20:53:30+00:00",
      "days": -13.8118246875,
      "is_lower_bound": false,
      "measured_at": "2026-10-14T16:22:31.653000+00:00",
      "url": "https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-84m7-p3x7-pcfv"
    }
  }
}