CVE-2026-33252

Description

The Go MCP SDK used Go's standard encoding/json. Prior to version 1.4.1, the Go SDK's Streamable HTTP transport accepted browser-generated cross-site `POST` requests without validating the `Origin` header and without requiring `Content-Type: application/json`. In deployments without Authorization, especially stateless or sessionless configurations, this allows an arbitrary website to send MCP requests to a local server and potentially trigger tool execution. Version 1.4.1 contains a patch for the issue.

References

https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-89xv-2j6f-qhc8

https://github.com/modelcontextprotocol/go-sdk/commit/a433a831d6e5d5ac3b9e625a8095aa8eaa040dfc

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-14643

Details

Source: Mitre, NVD

Named Vulnerability: GO-2026-4773Named Vulnerability: GHSA-89xv-2j6f-qhc8

Risk Information

CVSS v2

CVSS v3

EPSS