Vulnerability details

CVE-2026-33252

modelcontextprotocol go-sdk

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

CVSS 3.1

7.1High

Official 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.

CVSS scores

Score	Version	Source	Vector
7.1High	3.1	CVEProject cvelistV5 (CNA) (GitHub_M)	`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L`

Affected products

Vendor	Product	Versions	Source
modelcontextprotocol	go-sdk	< 1.4.1	CVEProject cvelistV5 (CNA)

References and advisories

https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-89xv-2j6f-qhc8 x_refsource_CONFIRM
https://github.com/modelcontextprotocol/go-sdk/commit/a433a831d6e5d5ac3b9e625a8095aa8eaa040dfc x_refsource_MISC

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Details

Published: 2026-03-24
Last updated: 2026-03-24
State: Published
Assigner (CNA): GitHub_M

Exploit prediction (EPSS)

0.18%

Probability of exploitation in 30 days

7.7%

Percentile (among all CVEs)

SSVC assessment (CISA)

Automatable: No
Exploitation: None
Technical impact: Partial

Weaknesses (CWE)

CWE-352
Cross-Site Request Forgery (CSRF)