GHSA-89xv-2j6f-qhc8Published

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

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cve-program · CVE-2026-33252

Published

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.

Source published: 23 Mar 2026 23:44:16 UTC
Source modified: 24 Mar 2026 18:39:50 UTC
Saved here: 23 Oct 2026 15:48:27 UTC
Source terms: CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 3.1 · 7.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

euvd · EUVD-2026-14643

Published

Additional publisher context

EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

Original publisher date fields

datePublished: Mar 23, 2026, 11:44:16 PM

dateUpdated: Mar 24, 2026, 6:39:50 PM

1 related source bulletins · separate from aliases

RHSA-2026:21772: Red Hat Security Advisory: Red Hat OpenShift Dev Spaces 3.28.0 Release.

CVE-2025-14813 · CVE-2025-68121 · CVE-2026-0636 · CVE-2026-1525 · CVE-2026-1526 · CVE-2026-1528 · CVE-2026-1605 · CVE-2026-2229 · CVE-2026-2327 · CVE-2026-5588 · CVE-2026-26996 · CVE-2026-27904 · CVE-2026-29074 · CVE-2026-30827 · CVE-2026-31802 · CVE-2026-32141 · CVE-2026-32280 · CVE-2026-32282 · CVE-2026-32305 · CVE-2026-33252 · CVE-2026-33810 · CVE-2026-34742 · CVE-2026-35051 · CVE-2026-39858 · CVE-2026-40477 · CVE-2026-40478 · CVE-2026-40611 · CVE-2026-40895 · CVE-2026-40912 · CVE-2026-40972 · CVE-2026-40973 · CVE-2026-40975 · CVE-2026-41240 · CVE-2026-42033 · CVE-2026-42035 · CVE-2026-42039 · CVE-2026-42041 · CVE-2026-42043 · CVE-2026-42044

Source published: Mar 23, 2026, 11:44:16 PM (timezone not stated)
Source modified: Mar 24, 2026, 6:39:50 PM (timezone not stated)
Saved here: 13 Nov 2026 09:06:08 UTC
Source terms: ENISA EUVD · source terms and attribution apply

Original source record · Cite this exact observation · Complete original publisher JSON

Source: euvd · ENISA EUVD · source terms and attribution apply. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

EUVD CVSS 3.1 · 7.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

nvd · CVE-2026-33252

Published

Additional publisher context

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Analyzed

Weakness classifications: CWE-352

Original publisher date fields

published: 2026-03-24T00:16:30.017

lastModified: 2026-06-17T10:37:11.830

1 source CPE criteria · context only

cpe:2.3:a:lfprojects:mcp_go_sdk:*:*:*:*:*:*:*:*

The original JSON retains the logical configuration operators, exclusions and version bounds.

Source published: 24 Mar 2026 00:16:30 UTC
Source modified: 17 Jun 2026 10:37:11 UTC
Saved here: 25 Oct 2026 08:17:18 UTC
Source terms: NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

Source: nvd · NIST NVD usage terms; underlying source attribution retained. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 3.1 · [email protected] · Secondary · 7.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

CVSS 3.1 · [email protected] · Primary · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

osv · GHSA-89xv-2j6f-qhc8

Published

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. #### Impact: A 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. #### Fix: The 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. Note: v1.4.1 requires Go 1.25 or later. #### Credits: Thank you to Lê Minh Quân for reporting the issue.

Source published: 19 Mar 2026 16:42:40 UTC
Source modified: 10 Sep 2026 03:50:38 UTC
Saved here: 24 Oct 2026 13:19:41 UTC
Source terms: GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L

Publisher rating · HIGH

osv · GO-2026-4773

Published

Cross-Site Tool Execution for HTTP Servers without Authorizatrion in github.com/modelcontextprotocol/go-sdk

Source published: 23 Mar 2026 18:14:51 UTC
Source modified: 25 Mar 2026 15:29:12 UTC
Saved here: 24 Oct 2026 13:19:41 UTC
Source terms: OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

Source: osv · OSV · upstream source license applies. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.