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.experiment…
Published: 2026-07-15 · CVSS: 7.6 · CVSS 3.1
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7