MCP Python SDK: Experimental task handlers allow any client to access and cancel other clients' tasks

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-52870
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-15 20:17:38 UTC
Updated2026-07-17 18:07:07 UTC
DescriptionThe 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.

Risk And Classification

Primary CVSS: v3.1 7.6 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L

EPSS: 0.002230000 probability, percentile 0.130110000 (date 2026-07-20)

Problem Types: CWE-862 | CWE-862 CWE-862: Missing Authorization

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.6HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L
3.1CNADECLARED7.6HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Lfprojects Mcp Python Sdk All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Modelcontextprotocol Python-sdk affected >= 1.23.0, < 1.27.2 Not specified

References

ReferenceSourceLinkTags
github.com/modelcontextprotocol/python-sdk/pull/2720 [email protected] github.com Issue Tracking, Patch
github.com/modelcontextprotocol/python-sdk/commit/62137874ff26dd74d2fea8... [email protected] github.com Patch
github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2 [email protected] github.com Release Notes
github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-hvrp... [email protected] github.com Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

© CVE.report 2026

Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. It is the responsibility of user to evaluate the accuracy, completeness or usefulness of any information, opinion, advice or other content. EACH USER WILL BE SOLELY RESPONSIBLE FOR ANY consequences of his or her direct or indirect use of this web site. ALL WARRANTIES OF ANY KIND ARE EXPRESSLY DISCLAIMED. This site will NOT BE LIABLE FOR ANY DIRECT, INDIRECT or any other kind of loss.

CVE, CWE, and OVAL are registred trademarks of The MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. This site includes MITRE data granted under the following license.

Free CVE JSON API cve.report/api

CVE.report and Source URL Uptime Status status.cve.report