CVE-2026-34742

HighCVSS 8.1/10Last modified Jul 24, 2026

Description

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.

Metrics

CVSS 3.1 8.1/10CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Weakness enumeration

CWE-1188

Affected software

No affected versions have been published.

Timeline

Published: Apr 2, 2026
Last modified: Jul 24, 2026
NVD status: Modified

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