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
lfprojects: mcp python sdk
References4
- github.com/modelcontextprotocol/python-sdk/security/advisories/… Vendor Advisory
- github.com/modelcontextprotocol/python-sdk/commit/62137874ff26d… Patch
- github.com/modelcontextprotocol/python-sdk/pull/2720 Issue TrackingPatch
- github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2 Release Notes
Metrics
- CVSS 3.1
-
7.6
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L - EPSS — exploit probability
- 0% percentile: 33 · as of 15 November 2026
- CWE
- CWE-862
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