CVE-2026-33252 — MCP Go SDK Allows Cross-Site Tool Execution for HTTP Servers without Authorizatrion
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 val…
Published: 2026-03-23 · CVSS: 7.1 · CVSS 3.1
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7