Vulnerability · Published Mar 23, 2026 · Assigned by GitHub_M
CVE-2026-33252MCP Go SDK Allows Cross-Site Tool Execution for HTTP Servers without Authorizatrion
High 7.1
In plain English
A high-severity cross-site request forgery in go-sdk from modelcontextprotocol. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 8% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/modelcontextprotocol/go-sdk | 1.4.1 | GHSA-89xv-2j6f-qhc8 |
| Go | github.com/modelcontextprotocol/go-sdk | 1.4.1 | GO-2026-4773 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| modelcontextprotocol | go-sdk | < 1.4.1 |
Weakness: CWE-352 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L