CVE-2026-59950: mcp python sdk — Fix

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.

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CVSS v3.1 Score

8.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

EPSS — Exploit Prediction

0.0015

Probability of exploitation

0.05%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-346 CWE-346

CWE-1385 CWE-1385

Affected Products

Vendor	Product	Versions
lfprojects	mcp_python_sdk	< 1.28.1

References

Advisories & Patches

https://github.com/modelcontextprotocol/python-sdk/commit/777b8d06710c140e3606b0d4598e2aa48546c266 https://github.com/modelcontextprotocol/python-sdk/pull/2992 https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-vj7q-gjh5-988w

Other References

https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.28.1

Frequently Asked Questions

What is CVE-2026-59950? +

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. It has a CVSS v3.1 base score of 8.1 (HIGH).

How severe is CVE-2026-59950? +

CVE-2026-59950 has a CVSS v3.1 score of 8.1 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0015, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-59950? +

CVE-2026-59950 affects products from lfprojects, specifically: mcp_python_sdk. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-59950? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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