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

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Summary

CVECVE-2026-33252
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-03-24 00:16:30 UTC
Updated2026-04-15 16:33:12 UTC
DescriptionThe 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.

Risk And Classification

Primary CVSS: v3.1 6.5 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

Problem Types: CWE-352 | CWE-352 CWE-352: Cross-Site Request Forgery (CSRF)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
3.1[email protected]Secondary7.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L
3.1CNADECLARED7.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Lfprojects Mcp Go Sdk All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Modelcontextprotocol Go-sdk affected < 1.4.1 Not specified

References

ReferenceSourceLinkTags
github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-89xv-2j6... [email protected] github.com Patch, Vendor Advisory
github.com/modelcontextprotocol/go-sdk/commit/a433a831d6e5d5ac3b9e625a80... [email protected] github.com Patch
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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