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Vulnerability record · CVE-2026-59950 · published 15 July 2026

CVE-2026-59950: Lfprojects mcp python sdk origin validation error vulnerability

Lfprojects · Mcp Python Sdk

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.

7.6 CVSS 4.0 High EPSS 0.23% · top 87.5% CWE-346 · Origin validation errorCWE-1385 · CWE-1385
7.6CVSS 4.0 base score
0.23%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
17 Jul 2026Last modified by NVD

Description

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.

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/modelcontextprotocol/python-sdk/commit/777b8d06710c140e3606b0d4598e2aa48546c266 Patch
https://github.com/modelcontextprotocol/python-sdk/pull/2992 Issue TrackingPatch
https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.28.1 Release Notes
https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-vj7q-gjh5-988w Vendor Advisory

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Source: NIST National Vulnerability Database (record CVE-2026-59950), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.