CVE-2026-52870

Analyzed Analyzed - Analysis Complete

Remote Task Access in MCP Python SDK

Publication date: 2026-07-15

Last updated on: 2026-07-17

Assigner: GitHub, Inc.

Description

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.

CVSS Scores

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Meta Information

Published

2026-07-15

Last Modified

2026-07-17

Generated

2026-08-05

AI Q&A

2026-07-16

EPSS Evaluated

2026-08-03

NVD

CVE-2026-52870

EUVD

EUVD-2026-44797

Affected Vendors & Products

Vendor	Product	Version / Range
lfprojects	mcp_python_sdk	From 1.23.0 (inc) to 1.27.2 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-862	The product does not perform an authorization check when an actor attempts to access a resource or perform an action.

Attack-Flow Graph

Executive Summary

This vulnerability affects the MCP Python SDK versions 1.23.0 to 1.27.1. Default handlers for task operations like tasks/list, tasks/get, tasks/result, and tasks/cancel do not verify which session created a task. This allows any connected client to access, read results from, or cancel tasks belonging to other clients when the experimental tasks feature is enabled.

Detection Guidance

Check if the MCP Python SDK version is between 1.23.0 and 1.27.1 using pip show mcp or pip list. If the experimental tasks feature is enabled, verify if task handlers lack session-based scoping by inspecting server logs for unauthorized task access attempts or unexpected task enumeration.

Impact Analysis

An attacker could enumerate all tasks, read sensitive task results or data intended for other clients, and cancel tasks. This could lead to unauthorized access to confidential information, disruption of services, or manipulation of task outcomes affecting integrity and availability.

Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, violating confidentiality requirements in GDPR and HIPAA. It may result in data breaches, non-compliance with data protection regulations, and potential legal consequences due to exposure of personal or health information.

Mitigation Strategies

Upgrade the MCP Python SDK to version 1.27.2 or later. Alternatively, disable the experimental tasks feature if upgrading is not feasible. Implement custom handlers with session validation to restrict task access.

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