{"cve":"CVE-2026-33252","nvd":{"published":"2026-03-24T00:16:30.017","modified":"2026-06-17T10:37:11.830","status":"Analyzed","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_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N","score":6.5},"cwes":["CWE-352"],"references":["https://github.com/modelcontextprotocol/go-sdk/commit/a433a831d6e5d5ac3b9e625a8095aa8eaa040dfc","https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-89xv-2j6f-qhc8"],"products":["lfprojects:mcp_go_sdk"],"source":"nvd","synced_at":"2026-10-19T22:26:19.218427112+00:00"},"epss":{"cve":"CVE-2026-33252","score":0.00181,"percentile":0.07679,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-89xv-2j6f-qhc8","url":"https://osv.dev/vulnerability/GHSA-89xv-2j6f-qhc8","summary":"Cross-Site Tool Execution for HTTP Servers without Authorizatrion in github.com/modelcontextprotocol/go-sdk","modified":"2026-09-10T03:50:38.202400539Z","packages":[{"ecosystem":"Go","name":"github.com/modelcontextprotocol/go-sdk","purl":"pkg:golang/github.com/modelcontextprotocol/go-sdk","ranges":["<1.4.1"],"fixed":["1.4.1"]}]},{"id":"GO-2026-4773","url":"https://osv.dev/vulnerability/GO-2026-4773","summary":"Cross-Site Tool Execution for HTTP Servers without Authorizatrion in github.com/modelcontextprotocol/go-sdk","modified":"2026-03-25T15:29:12.946702Z","packages":[{"ecosystem":"Go","name":"github.com/modelcontextprotocol/go-sdk","purl":"pkg:golang/github.com/modelcontextprotocol/go-sdk","ranges":["<1.4.1"],"fixed":["1.4.1"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}