The Go MCP SDK used Go's standard encoding/json.
Date: 2026-04
Affected: lfprojects/mcp_go_sdk
Attack vector: other
Category: vulnerability-disclosure
Severity: High
CVE: CVE-2026-33252
CVE-2026-34742
CWE: CWE-1188
CWE-352
CVSS: 8.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N)

The Go MCP SDK used Go's standard encoding/json. Prior to version 1.4.0, the Model Context Protocol (MCP) Go SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication with StreamableHTTPHandler or SSEHandler, a malicious website could exploit DNS rebinding to bypass same-origin policy restrictions and send requests to the local MCP server. This could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the user in those limited circumstances. This issue has been patched in version 1.4.0.


Mitigations:

Architectural layers (MAESTRO):