8.7
High
CVE-2025-53366 The MCP Python SDK, called `mcp` on PyPI, is a Python implementation of the Model Context Protocol (MCP)
Description
The MCP Python SDK, called `mcp` on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to version 1.9.4, a validation error in the MCP SDK can cause an unhandled exception when processing malformed requests, resulting in service unavailability (500 errors) until manually restarted. Impact may vary depending on the deployment conditions, and presence of infrastructure-level resilience measures. Version 1.9.4 contains a patch for the issue.
Affected products and versions
| Product | Affected versions | Fixed in |
|---|---|---|
| python-sdk 1.9 | earliest → < 1.9.4 | 1.9.4 |
Other CVEs of python-sdk
The 11 CVEs of python-sdk →
CVE-2026-116686
The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients
6.5
Medium
CVE-2026-116685
The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients
5.9
Medium
CVE-2026-116684
The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients
6.8
Medium
CVE-2026-109527
The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients
7.5
High