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National Vulnerability Database

National Vulnerability Database

NVD

National Vulnerability Database
  1. Vulnerabilities

CVE-2026-34742 Detail

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

 
NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

Nist CVSS score does not match with CNA score
CNA:  GitHub, Inc.
CVSS-B 7.6 HIGH
Vector:  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

References to Advisories, Solutions, and Tools

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URL Source(s) Tag(s)
https://access.redhat.com/errata/RHSA-2026:21772 redhat-SADP
https://access.redhat.com/security/cve/CVE-2026-34742 redhat-SADP
https://bugzilla.redhat.com/show_bug.cgi?id=2454608 redhat-SADP
https://github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6d GitHub, Inc. Patch 
https://github.com/modelcontextprotocol/go-sdk/pull/760 GitHub, Inc. Issue Tracking  Patch 
https://github.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0 GitHub, Inc. Release Notes 
https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-xw59-hvm2-8pj6 GitHub, Inc. Vendor Advisory 
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34742.json redhat-SADP

Weakness Enumeration

CWE-ID CWE Name Source
CWE-1188 Insecure Default Initialization of Resource GitHub, Inc.   redhat-SADP  

Known Affected Software Configurations Switch to CPE 2.2

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Change History

5 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2026-34742
NVD Published Date:
04/02/2026
NVD Last Modified:
06/29/2026
Source:
GitHub, Inc.