GHSA-89xv-2j6f-qhc8
Cross-Site Tool Execution for HTTP Servers without Authorizatrion in github.com/modelcontextprotocol/go-sdk
Quick fix
GHSA-89xv-2j6f-qhc8 — github.com/modelcontextprotocol/go-sdk: upgrade to the fixed version with the command below.
go get github.com/modelcontextprotocol/go-sdk@v1.4.1Details
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.
Are you affected?
Enter the version of the package you're using.
Affected packages
0Fixed in: 1.4.1go get github.com/modelcontextprotocol/go-sdk@v1.4.1References
- https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-89xv-2j6f-qhc8[WEB]
- https://nvd.nist.gov/vuln/detail/CVE-2026-33252[ADVISORY]
- https://github.com/modelcontextprotocol/go-sdk/commit/a433a831d6e5d5ac3b9e625a8095aa8eaa040dfc[WEB]
- https://github.com/modelcontextprotocol/go-sdk[PACKAGE]