CVE-2026-59950
Published:July 15, 2026
Updated:July 30, 2026
The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to 1.28.1, the deprecated mcp.server.websocket.websocket_server transport accepted WebSocket handshakes without applying Host or Origin header validation, leaving no SDK-level way to restrict which origins could connect to applications that exposed that transport. This issue is fixed in version 1.28.1.
Affected Packages
mcp (CONDA):
Affected version(s) >=1.3.0 <1.28.1Fix Suggestion:
Update to version 1.28.1mcp (CONDA):
Affected version(s) >=1.3.0 <1.28.1Fix Suggestion:
Update to version 1.28.1https://github.com/modelcontextprotocol/python-sdk.git (GITHUB):
Affected version(s) >=v1.0.0 <v1.28.1Fix Suggestion:
Update to version v1.28.1mcp (PYTHON):
Affected version(s) >=0.1.0 <1.28.1Fix Suggestion:
Update to version 1.28.1mcp (PYTHON):
Affected version(s) >=0.1.0 <1.28.1Fix Suggestion:
Update to version 1.28.1Related Resources (9)
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Contact UsCVSS v4
Base Score:
7.6
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
PRESENT
Privileges Required
NONE
User Interaction
PASSIVE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
HIGH
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
8.1
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
NONE
EPSS
Base Score:
0.15