Summaryinfo

A vulnerability categorized as problematic has been discovered in modelcontextprotocol go-sdk up to 1.4.0. Affected is an unknown function of the component Content-Type Handler. The manipulation results in cross-site request forgery. This vulnerability is identified as CVE-2026-33252. The attack can be executed remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in modelcontextprotocol go-sdk up to 1.4.0. It has been classified as problematic. Affected is an unknown functionality of the component Content-Type Handler. The manipulation with an unknown input leads to a cross-site request forgery vulnerability. CWE is classifying the issue as CWE-352. The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request. This is going to have an impact on integrity. CVE summarizes:

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 advisory is available at github.com. This vulnerability is traded as CVE-2026-33252 since 03/18/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. The technical details are unknown and an exploit is not available.

Upgrading to version 1.4.1 eliminates this vulnerability. Applying the patch a433a831d6e5d5ac3b9e625a8095aa8eaa040dfc is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

• modelcontextprotocol

Name

• go-sdk

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4.0

License

• open-source

Website

• Product: https://github.com/modelcontextprotocol/go-sdk/

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