CVE-2026-33252CWE-352

MCP Go SDK Allows Cross-Site Tool Execution for HTTP Servers without Authorizatrion

High · published March 23, 2026

CVSS v3.1
7.1
EPSS
0%
Percentile
11.9
In the wild
Unconfirmed
What it is

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 record
Technical detail
CVSS v3.1
7.1 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L
CVSS v4.0
Not supplied
EPSS
0.00220 · 11.9th percentile
Weakness
CWE-352 · Cross-Site Request Forgery (CSRF)
Published
2026-03-23T23:44Z
EPSS history
Timeline
  • 23 MAR 23:44Z
    MCP Go SDK Allows Cross-Site Tool Execution for HTTP Servers without Authorizatrion
    cvelistv5