CVE-2025-53366
July 04, 2025
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 Packages
https://github.com/modelcontextprotocol/python-sdk.git (GITHUB):
Affected version(s) >=v0.2.0 <v1.9.4Fix Suggestion:
Update to version v1.9.4mcp (PYTHON):
Affected version(s) >=0.1.0 <1.9.4Fix Suggestion:
Update to version 1.9.4mcp (PYTHON):
Affected version(s) >=0.1.0 <1.9.4Fix Suggestion:
Update to version 1.9.4Related Resources (6)
Do you need more information?
Contact UsCVSS v4
Base Score:
8.7
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
7.5
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Weakness Type (CWE)
Uncaught Exception
EPSS
Base Score:
0.03
