PYSEC-2026-1618

Vulnerability from pysec - Published: 2026-07-07 16:02 - Updated: 2026-07-07 17:24
VLAI
Details

If a client deliberately triggers an exception after establishing a streamable HTTP session, this can lead to an uncaught ClosedResourceError on the server side, causing the server to crash and requiring a restart to restore service. Impact may vary depending on the deployment conditions, and presence of infrastructure-level resilience measures.

Thank you to Rich Harang for reporting this issue.

Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Impacted products
Name purl
mcp pkg:pypi/mcp
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "mcp",
        "purl": "pkg:pypi/mcp"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.10.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.9.1",
        "1.0.0",
        "1.1.0",
        "1.1.1",
        "1.1.2",
        "1.1.3",
        "1.2.0",
        "1.2.0rc1",
        "1.2.1",
        "1.3.0",
        "1.3.0rc1",
        "1.4.0",
        "1.4.1",
        "1.5.0",
        "1.6.0",
        "1.7.0",
        "1.7.1",
        "1.8.0",
        "1.8.1",
        "1.9.0",
        "1.9.1",
        "1.9.2",
        "1.9.3",
        "1.9.4"
      ]
    }
  ],
  "aliases": [
    "CVE-2025-53365",
    "GHSA-j975-95f5-7wqh"
  ],
  "details": "If a client deliberately triggers an exception after establishing a streamable HTTP session, this can lead to an uncaught ClosedResourceError on the server side, causing the server to crash and requiring a restart to restore service. Impact may vary depending on the deployment conditions, and presence of infrastructure-level resilience measures.\n\nThank you to Rich Harang for reporting this issue.",
  "id": "PYSEC-2026-1618",
  "modified": "2026-07-07T17:24:40.321367Z",
  "published": "2026-07-07T16:02:56.105116Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-j975-95f5-7wqh"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-53365"
    },
    {
      "type": "WEB",
      "url": "https://github.com/modelcontextprotocol/python-sdk/pull/967"
    },
    {
      "type": "WEB",
      "url": "https://github.com/modelcontextprotocol/python-sdk/commit/7b420656de48cfdb90b39eb582e60b6d55c2f891"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/modelcontextprotocol/python-sdk"
    },
    {
      "type": "WEB",
      "url": "https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.10.0"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/mcp"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-j975-95f5-7wqh"
    }
  ],
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "MCP Python SDK has Unhandled Exception in Streamable HTTP Transport, Leading to Denial of Service"
}


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