CVE-2026-52870 (GCVE-0-2026-52870)

Vulnerability from cvelistv5 – Published: 2026-07-15 20:07 – Updated: 2026-07-15 20:07
VLAI
Title
MCP Python SDK: Experimental task handlers allow any client to access and cancel other clients' tasks
Summary
The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). From 1.23.0 until 1.27.2, default handlers installed by server.experimental.enable_tasks() for tasks/list, tasks/get, tasks/result, and tasks/cancel operate only on task identifiers without recording the session that created each task, allowing any connected client to enumerate, read results from, consume messages for, or cancel other clients' tasks. This issue is fixed in version 1.27.2.
Severity
7.6 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L
CWE
Assigner
References
Impacted products
Vendor Product Version
modelcontextprotocol python-sdk Affected: >= 1.23.0, < 1.27.2
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{
  "containers": {
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      "affected": [
        {
          "product": "python-sdk",
          "vendor": "modelcontextprotocol",
          "versions": [
            {
              "status": "affected",
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            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). From 1.23.0 until 1.27.2, default handlers installed by server.experimental.enable_tasks() for tasks/list, tasks/get, tasks/result, and tasks/cancel operate only on task identifiers without recording the session that created each task, allowing any connected client to enumerate, read results from, consume messages for, or cancel other clients\u0027 tasks. This issue is fixed in version 1.27.2."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 7.6,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "LOW",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-862",
              "description": "CWE-862: Missing Authorization",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-15T20:07:53.500Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-hvrp-rf83-w775",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-hvrp-rf83-w775"
        },
        {
          "name": "https://github.com/modelcontextprotocol/python-sdk/pull/2720",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/modelcontextprotocol/python-sdk/pull/2720"
        },
        {
          "name": "https://github.com/modelcontextprotocol/python-sdk/commit/62137874ff26dd74d2fea80ff528a7fd9ca7a5e7",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/modelcontextprotocol/python-sdk/commit/62137874ff26dd74d2fea80ff528a7fd9ca7a5e7"
        },
        {
          "name": "https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2"
        }
      ],
      "source": {
        "advisory": "GHSA-hvrp-rf83-w775",
        "discovery": "UNKNOWN"
      },
      "title": "MCP Python SDK: Experimental task handlers allow any client to access and cancel other clients\u0027 tasks"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-52870",
    "datePublished": "2026-07-15T20:07:53.500Z",
    "dateReserved": "2026-06-08T21:44:27.364Z",
    "dateUpdated": "2026-07-15T20:07:53.500Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
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      "date": "2026-06-14",
      "epss": "0.00043",
      "percentile": "0.13452"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-52870\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-07-15T20:17:38.577\",\"lastModified\":\"2026-07-15T20:54:43.733\",\"vulnStatus\":\"Undergoing Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). From 1.23.0 until 1.27.2, default handlers installed by server.experimental.enable_tasks() for tasks/list, tasks/get, tasks/result, and tasks/cancel operate only on task identifiers without recording the session that created each task, allowing any connected client to enumerate, read results from, consume messages for, or cancel other clients\u0027 tasks. This issue is fixed in version 1.27.2.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"modelcontextprotocol\",\"product\":\"python-sdk\",\"versions\":[{\"version\":\"\u003e= 1.23.0, \u003c 1.27.2\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L\",\"baseScore\":7.6,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"LOW\",\"availabilityImpact\":\"LOW\"},\"exploitabilityScore\":2.8,\"impactScore\":4.7}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-862\"}]}],\"references\":[{\"url\":\"https://github.com/modelcontextprotocol/python-sdk/commit/62137874ff26dd74d2fea80ff528a7fd9ca7a5e7\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/modelcontextprotocol/python-sdk/pull/2720\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-hvrp-rf83-w775\",\"source\":\"security-advisories@github.com\"}]}}"
  }
}



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