Model Context Protocol Go SDK: DNS Rebinding Protection Disabled by Default for Servers Running on Localhost

MITRE NVD CVE.ORG JSON API Print: PDF PDF

Summary

CVECVE-2026-34742
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-02 19:21:33 UTC
Updated2026-07-15 02:20:34 UTC
DescriptionThe 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.

Risk And Classification

Primary CVSS: v4.0 7.6 HIGH from [email protected]

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

EPSS: 0.004550000 probability, percentile 0.366320000 (date 2026-07-15)

Problem Types: CWE-1188 | CWE-1188 CWE-1188: Insecure Default Initialization of Resource | CWE-1188 Initialization of a Resource with an Insecure Default

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary7.6HIGHCVSS: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/C...
4.0CNADECLARED7.6HIGHCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
3.1[email protected]Primary8.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
3.1ADPCVSS8HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N
3.10b0ca135-0b70-47e7-9f44-1890c2a1c46cSecondary8HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
None
User Interaction
Passive
Confidentiality
High
Integrity
High
Availability
None
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

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

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Lfprojects Mcp Go Sdk All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Modelcontextprotocol Go-sdk affected < 1.4.0 Not specified
ADP Red Hat Red Hat OpenShift Dev Spaces 3.28 unaffected 1779829736 * rpm Not specified
ADP Red Hat Migration Toolkit For Virtualization Not specified Not specified
ADP Red Hat Migration Toolkit For Virtualization Not specified Not specified
ADP Red Hat Migration Toolkit For Virtualization Not specified Not specified
ADP Red Hat Migration Toolkit For Virtualization Not specified Not specified
ADP Red Hat Migration Toolkit For Virtualization Not specified Not specified
ADP Red Hat OpenShift Lightspeed Not specified Not specified
ADP Red Hat OpenShift Serverless Not specified Not specified
ADP Red Hat OpenShift Serverless Not specified Not specified
ADP Red Hat Red Hat OpenShift AI RHOAI Not specified Not specified

References

ReferenceSourceLinkTags
github.com/modelcontextprotocol/go-sdk/pull/760 [email protected] github.com Issue Tracking, Patch
github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-xw59-hvm... [email protected] github.com Vendor Advisory
bugzilla.redhat.com/show_bug.cgi 0b0ca135-0b70-47e7-9f44-1890c2a1c46c bugzilla.redhat.com
github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976... [email protected] github.com Patch
github.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0 [email protected] github.com Release Notes
access.redhat.com/errata/RHSA-2026:21772 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34742.json 0b0ca135-0b70-47e7-9f44-1890c2a1c46c security.access.redhat.com
access.redhat.com/security/cve/CVE-2026-34742 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

SourceTimeEvent
ADP2026-04-02T19:06:39.830ZReported to Red Hat.
ADP2026-04-02T18:32:34.781ZMade public.

Solutions

ADP: RHSA-2026:21772: Red Hat OpenShift Dev Spaces 3.28

Workarounds

ADP: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

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