CVE-2026-52870 MCP Python SDK: Experimental task handlers allow any client to access and cancel other clients' tasks

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.enabletasks for tasks/list, tasks/get, tasks/result, and tasks/cancel operate only on task identifiers without recordin...

CVE-2026-52870

The MCP Python SDK (package mcp on PyPI) has a vulnerability in versions 1.23.0–1.27.1 where default handlers installed by server.experimental.enable_tasks() for tasks/list, tasks/get, tasks/result, and tasks/cancel only operate on task identifiers and do not record the session that created each ...