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CVE-2026-33252

NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-33252

Severity

7.1

High

CVSS V3

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Summary

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

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.

References

Affected packages

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