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Back to active CVEs
High · CVSS 7.6CVE-2026-34742

Model Context Protocol Go SDK: DNS Rebinding Protection Disabled by Default for Servers Running on LocalhostCVE-2026-34742

Answer in brief

CVE-2026-34742 records a High severity (CVSS 7.6) vulnerability in Model Context Protocol Go SDK: DNS Rebinding Protection Disabled by Default for Servers Running on Localhost. The current sources do not mark it as known exploited. The current feed maps modelcontextprotocol/go-sdk (generic), Red Hat/migration-toolkit-virtualization/mtv-cli-download-rhel9 (generic), Red Hat/mtv-candidate/mtv-api-rhel9 (generic), Red Hat/mtv-candidate/mtv-cli-download-rhel9 (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Apr 2, 2026Updated Jul 15, 2026Source checked Nov 4, 2026First seen by HOL Jul 15, 2026Material review Jul 15, 2026
Upstream Advisory

Key facts

Risk
High · CVSS 7.6
Exploitation
Not marked as known exploited
Affected software
8 mapped packages or products
Fix availability
Available

Why this deserves its current priority

CVSS is 7.6. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps modelcontextprotocol/go-sdk (generic), Red Hat/migration-toolkit-virtualization/mtv-cli-download-rhel9 (generic), Red Hat/mtv-candidate/mtv-api-rhel9 (generic), Red Hat/mtv-candidate/mtv-cli-download-rhel9 (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
modelcontextprotocol/go-sdkgeneric<1.4.01.4.0
Red Hat/migration-toolkit-virtualization/mtv-cli-download-rhel9generic*Not reported
Red Hat/mtv-candidate/mtv-api-rhel9generic*Not reported
Red Hat/mtv-candidate/mtv-cli-download-rhel9generic*Not reported
Red Hat/mtv-candidate/mtv-controller-rhel9generic*Not reported
Red Hat/mtv-candidate/mtv-operator-bundlegeneric*Not reported
Red Hat/openshift-serverless-1/kn-client-kn-rhel9generic*Not reported
Red Hat/openshift-serverless-1/kn-plugin-func-func-util-rhel9generic*Not reported

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for modelcontextprotocol/go-sdk, Red Hat/migration-toolkit-virtualization/mtv-cli-download-rhel9, Red Hat/mtv-candidate/mtv-api-rhel9.
  2. 2Review the reported fix. Update modelcontextprotocol/go-sdk to 1.4.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

  1. Published upstream

    Apr 2, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Jul 15, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Jul 15, 2026

Sources and claim methodology

  • Source referenceaccess.redhat.com
  • Source referenceaccess.redhat.com
  • Source referencebugzilla.redhat.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • Source referencesecurity.access.redhat.com
Upstream source 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.

Quoted source text, attributed separately from HOL analysis.

Record context

Vulnerability class
Tool Poisoning
EPSS
Not reported
CWE IDs
CWE-1188
Source
CVE List V5
Source checked
Nov 4, 2026
References
8 linked sources
Open source record