Описание
Cross-Site Tool Execution for HTTP Servers without Authorizatrion in github.com/modelcontextprotocol/go-sdk
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.
Impact:
A malicious website may have been able to send cross-site POST requests with Content-Type: text/plain, which due to CORS-safelisted properties would reach the MCP message handling without any CORS preflight barrier.
Fix:
The SDK was modified to perform Content-Type header validation for POST requests and introduced a configurable protection for verifying the origin of the request in commit a433a83. Users are advised to update to v1.4.1 to use this additional protection.
Note: v1.4.1 requires Go 1.25 or later.
Credits:
Thank you to Lê Minh Quân for reporting the issue.
Пакеты
github.com/modelcontextprotocol/go-sdk
<= 1.4.0
1.4.1
Связанные уязвимости
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.
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.