🛡️ CVE-2026-33252
🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-352 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L
CWE CWE-352
Public Exploit ✅ No
Source NVD
Published 2026-03-19
Updated 2026-06-15
Modified 2026-03-25

Affected Packages

Software From version Fixed in
github.com/modelcontextprotocol/go-sdk
mcp-go-sdk 1.4.1

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