CVE-2026-33252: Github.com/modelcontextprotocol/go sdk Cross-Site Tool Execution For HTTP Vulnerability
HIGHCVE-2026-33252 is a HIGH (CVSS 7.1) cross-site tool execution for http vulnerability (CWE-352: Cross-Site Request Forgery (CSRF)) affecting Github.com/modelcontextprotocol/go sdk libraries in the Go ecosystem. The issue involves cross-site tool execution for http servers without authorizatrion in github.com/modelcontextprotocol/go-sdk. Remediation is available by upgrading affected packages to version 1.4.1.
CVE-2026-33252 at a Glance
Security Impact
CVSS: 7.1
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L).
How to Fix CVE-2026-33252
To remediate this vulnerability, upgrade all affected Github.com/modelcontextprotocol/go sdk dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade github.com/modelcontextprotocol/go-sdk to 1.4.1Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for github.com/modelcontextprotocol/go-sdkHow to Check if You Are Affected
To determine whether your application is affected by CVE-2026-33252, inspect your project dependencies for Github.com/modelcontextprotocol/go sdk:
inspect dependencies for github.com/modelcontextprotocol/go-sdkAnalyze the terminal output to locate any version of Github.com/modelcontextprotocol/go sdk in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.4.1), your application is affected.
Note: Verify declared build manifests and deployed runtime container environments.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-352: Cross-Site Request Forgery (CSRF), where the web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor. In Github.com/modelcontextprotocol/go sdk, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-33252 Affected Github.com/modelcontextprotocol/go sdk Versions
1 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
github.com/modelcontextprotocol/go-sdk
|
Go |
< 1.4.1
|
1.4.1
|
References
Frequently Asked Questions
What is CVE-2026-33252?
Which Github.com/modelcontextprotocol/go sdk versions are affected?
What version fixes CVE-2026-33252?
Is github.com/modelcontextprotocol/go-sdk affected?
What is the CVSS score of CVE-2026-33252?
What CWE is associated with CVE-2026-33252?
How can I check Go dependencies for CVE-2026-33252?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-89xv-2j6f-qhc8",
"modified" : "2026-03-25T20:48:22Z",
"published" : "2026-03-19T16:42:40Z",
"aliases" : [ "CVE-2026-33252" ],
"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.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/modelcontextprotocol/go-sdk"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "1.4.1"
} ]
} ],
"database_specific" : {
"last_known_affected_version_range" : "<= 1.4.0"
}
} ],
"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" ],
"severity" : "HIGH",
"github_reviewed" : true,
"github_reviewed_at" : "2026-03-19T16:42:40Z",
"nvd_published_at" : "2026-03-24T00:16:30Z"
}
}