{"id":"CVE-2026-33252","summary":"MCP Go SDK Allows Cross-Site Tool Execution for HTTP Servers without Authorizatrion","details":"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.","aliases":["GHSA-89xv-2j6f-qhc8","GO-2026-4773"],"modified":"2026-04-02T13:27:13.540629Z","published":"2026-03-23T23:44:16.106Z","related":["CGA-xfc9-vhjg-vr43","SUSE-SU-2026:1135-1"],"database_specific":{"cwe_ids":["CWE-352"],"cna_assigner":"GitHub_M","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33252.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33252.json"},{"type":"FIX","url":"https://github.com/modelcontextprotocol/go-sdk/commit/a433a831d6e5d5ac3b9e625a8095aa8eaa040dfc"},{"type":"ADVISORY","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"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/modelcontextprotocol/go-sdk","events":[{"introduced":"0"},{"fixed":"580f2a09be5c5b7ed4d868aa74ad1019dfd5160a"}],"database_specific":{"versions":[{"introduced":"0"},{"fixed":"1.4.1"}]}}],"versions":["v0.1.0","v0.2.0","v0.3.0","v0.3.1","v0.4.0","v0.5.0","v0.6.0","v0.7.0","v0.8.0","v1.0.0","v1.1.0","v1.1.0-pre.1","v1.1.0-pre.2","v1.2.0","v1.2.0-pre.1","v1.2.0-pre.2","v1.3.0","v1.3.0-pre.1","v1.3.1","v1.4.0","v1.5.0-pre.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33252.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L"}]}