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TI-2026-26986 Aliases CVE-2026-34742GHSA-xw59-hvm2-8pj6

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

Priority LOW 36CWE-1188Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Passive
Attack complexity
Low
Attack requirements
Present
Impact type
—
Confidentiality · integrity · availability
High · High · None
Fix status
Partial Red Hat: 1 fixed, 2 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00472 41st percentileScored 2026-11-07
Fix Partial go-sdk (modelcontextprotocol): 1.4.0github.com/modelcontextprotocol/go-sdk (Go): 1.4.0Red Hat: 1 advisoryRed Hat: 1 fixed, 2 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MLflowgo-sdkbefore 1.4.01.4.0Patch availableCNA
—github.com/modelcontextprotocol/go-sdk (Go)before 1.4.01.4.0Patch availableGHSA-xw59-hvm2-8pj6
  • go-sdk VendorMLflow Affected before 1.4.0 Fixed in 1.4.0 Patch available CNA
  • github.com/modelcontextprotocol/go-sdk (Go) Vendor— Affected before 1.4.0 Fixed in 1.4.0 Patch available GHSA-xw59-hvm2-8pj6

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:lfprojects:mcp_go_sdk:*:*:*:*:*:*:*:*before 1.4.0VulnerableMLflow
  • cpe:2.3:a:lfprojects:mcp_go_sdk:*:*:*:*:*:*:*:* Versions before 1.4.0 Vulnerable ·MLflow

Remediation

  • Fix · CNA go-sdk (modelcontextprotocol) Fixed in 1.4.0
  • Fix · GHSA-xw59-hvm2-8pj6 github.com/modelcontextprotocol/go-sdk (Go) Fixed in 1.4.0 Advisory →

Red Hat 1 advisory

  • RHSA-2026:21772 Released 2026-05-28 · Red Hat rating Important
    Red Hat OpenShift Dev Spaces 3.28.0 Release.
    • Red Hat OpenShift Dev Spaces 3.28 registry.redhat.io/devspaces/code-rhel9, registry.redhat.io/devspaces/dashboard-rhel9, registry.redhat.io/devspaces/openvsx-rhel9 +3

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Migration Toolkit for VirtualizationAffectedNo fix planned: Will not fix
OpenShift ServerlessAffectedNo fix yet
Red Hat OpenShift Dev Spaces 3.28Fixed RHSA-2026:21772
Not affected: 3 products
  • OpenShift Lightspeed
  • Red Hat OpenShift AI (RHOAI)
  • Red Hat OpenShift Dev Spaces 3.28

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-34742
  2. 2026-10-03 Alias added: GHSA-xw59-hvm2-8pj6
  3. 2026-10-05 EPSS moved to the 50th–90th percentile
  4. 2026-10-25 EPSS moved to the below the 50th percentile

References

Patch 2

Advisory 2

Other 6

  • TI-2026-22240 MCP Go SDK Vulnerable to Improper Handling of Case Sensitivity CVSS 4.0HIGH 7.0
  • TI-2026-25670 MCP Go SDK Allows Cross-Site Tool Execution for HTTP Servers without Authorizatrion CVSS 3.1HIGH 7.1

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences