{"schema_version":"1.7.5","id":"GHSA-89xv-2j6f-qhc8","published":"2026-03-19T16:42:40Z","modified":"2026-03-25T21:06:07.072062Z","aliases":["CVE-2026-33252","GO-2026-4773"],"related":["CGA-xfc9-vhjg-vr43"],"summary":"Cross-Site Tool Execution for HTTP Servers without Authorizatrion in github.com/modelcontextprotocol/go-sdk","details":"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.\n\n#### Impact:\n\nA malicious website may have been able to send cross-site POST requests with `Content-Type: text/plain`, which due to CORS-safelisted properties would reach the MCP message handling without any CORS preflight barrier.\n\n#### Fix:\n\nThe SDK was modified to perform `Content-Type` header validation for POST requests and introduced a configurable protection for verifying the origin of the request in commit a433a83. Users are advised to update to v1.4.1 to use this additional protection.\n\nNote: v1.4.1 requires Go 1.25 or later.\n\n#### Credits:\n\nThank you to Lê Minh Quân for reporting the issue.","affected":[{"package":{"name":"github.com/modelcontextprotocol/go-sdk","ecosystem":"Go","purl":"pkg:golang/github.com/modelcontextprotocol/go-sdk"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.4.1"}]}],"database_specific":{"last_known_affected_version_range":"<= 1.4.0","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-89xv-2j6f-qhc8/GHSA-89xv-2j6f-qhc8.json"}}],"references":[{"type":"WEB","url":"https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-89xv-2j6f-qhc8"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33252"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/go-sdk/commit/a433a831d6e5d5ac3b9e625a8095aa8eaa040dfc"},{"type":"PACKAGE","url":"https://github.com/modelcontextprotocol/go-sdk"}],"database_specific":{"cwe_ids":["CWE-352"],"github_reviewed":true,"github_reviewed_at":"2026-03-19T16:42:40Z","nvd_published_at":"2026-03-24T00:16:30Z","severity":"HIGH"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L"}]}