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CVE PROGRAM SOURCE RECORD7.6 High

CVE-2026-52870

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

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

modelcontextprotocol python-sdk

  • >= 1.23.0, < 1.27.2affected

References