CVE-2026-34742

HIGH EPSS 33.7%

Published Apr 2, 20262mo ago · Modified Jun 17, 20261w ago

7.6 CVSS 4.0

High

Published Apr 2, 2026 2mo ago

Last Modified Jun 17, 2026 1w ago

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.

CVSS Details

Base Score

7.6

Exploitability

—

Impact

—

Vector string

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector Network

Attack Complexity Low

Privileges Required None

User Interaction P

Scope X

Threat Intelligence

EPSS Exploit Probability

33.7% percentile

Exploit & Patch Status

No Known Exploit

Patch Available

Weaknesses 1

CWE-1188

Affected Products 1

Vendor	Product	Version	Range
lfprojects	mcp_go_sdk	*	<1.4.0

References 4

github.com https://github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6d

Patch
github.com https://github.com/modelcontextprotocol/go-sdk/pull/760

Issue TrackingPatch
github.com https://github.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0

Release Notes
github.com https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-xw59-hvm2-8pj6

Vendor Advisory

Remediation

github.com https://github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6d

Patch
github.com https://github.com/modelcontextprotocol/go-sdk/pull/760

Issue TrackingPatch