CVE-2026-52870

HIGH

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

Title source: cna
STIX 2.1

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.

References (4)

Core 4

Scores

CVSS v3 7.6
EPSS 0.0024
EPSS Percentile 14.8%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact partial

Details

CWE
CWE-862
Status published
Products (3)
lfprojects/mcp_python_sdk 1.23.0 - 1.27.2
modelcontextprotocol/python-sdk >= 1.23.0, < 1.27.2
pypi/mcp 1.23.0 - 1.27.2PyPI
Published Jul 15, 2026
Tracked Since Jul 16, 2026