CVE-2026-59950: MCP Python SDK WebSocket server lacks Host and Origin validation

# CVE-2026-59950: MCP Python SDK WebSocket server lacks Host and Origin validation

https://gcdradar.vercel.app/incidents/cve-2026-59950-mcp-python-sdk-websocket-server-lacks-host-an · AIR-2026-0807 · closed 2026-07-15

- Lane: Patch now
- Severity: 2 (Disclosed vulnerability)
- Fix status: Fix status unknown
- First reported: 2026-07-15 (happened 2026-07-16)
- AI role: Attack on AI
- Products: MCP Python SDK
- CVE ids: CVE-2026-59950
- CVSS: 7.6

## Summary

The deprecated WebSocket server transport in the MCP Python SDK accepts handshakes without validating Host or Origin headers. This exposes applications exposing this transport to potential cross-site connection vulnerabilities.

## What to do

No action recorded; read the sources below and the vendor's advisory.

## Latest updates

- 2026-07-16: CVE-2026-59950: MCP Python SDK: WebSocket server transport does not support Host/Origin validation (https://github.com/advisories/GHSA-vj7q-gjh5-988w)
- 2026-07-15: CVE-2026-59950: The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). (https://nvd.nist.gov/vuln/detail/CVE-2026-59950)

## Sources

- 2026-07-15 NVD: CVE-2026-59950: The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). https://nvd.nist.gov/vuln/detail/CVE-2026-59950
- 2026-07-16 GitHub Advisory Database: CVE-2026-59950: MCP Python SDK: WebSocket server transport does not support Host/Origin validation https://github.com/advisories/GHSA-vj7q-gjh5-988w

Verify against the vendor's advisory before changing production. Data CC BY-SA 4.0, https://gcdradar.vercel.app.