{"id":"CVE-2026-34742","title":"github.com/modelcontextprotocol/go-sdk: Model Context Protocol (MCP) Go SDK: DNS rebinding vulnerability allows unauthorized access (CVE-20…","summary":"A flaw was found in the Model Context Protocol (MCP) Go SDK. When an HTTP-based MCP server is run on localhost without authentication, a malicious website can exploit a DNS rebinding vulnerability. This allows the attacker to bypass same-o…","severity":"high","cvss":8,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N","cvssSource":"vendor","cwe":"CWE-1188","vendor":"Red Hat","product":"Migration Toolkit for Virtualization","affected":["migration_toolkit_for_virtualization","openshift_serverless","openshift_dev_spaces 3.28"],"patched":["openshift_dev_spaces 3.28"],"published":"2026-04-02","updated":"2026-10-15","sourceUpdated":"2026-10-15T10:58:13+00:00","source":"CSAF","sourceUrl":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34742.json","references":[{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34742.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-34742"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2454608"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-34742"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34742"},{"url":"https://github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6d"},{"url":"https://github.com/modelcontextprotocol/go-sdk/pull/760"},{"url":"https://github.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0"},{"url":"https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-xw59-hvm2-8pj6"},{"url":"https://access.redhat.com/errata/RHSA-2026:21772"},{"url":"https://github.com/modelcontextprotocol/go-sdk"}],"tags":["csaf","vex","red-hat","osv","go"],"epss":0.00455,"epssPercentile":0.39278,"aliases":["GHSA-xw59-hvm2-8pj6","GO-2026-5771"],"ecosystem":"go","scores":{"vendor":8,"osv":8.1},"ingestedAt":"2026-07-21T19:04:59.717Z","slug":"CVE-2026-34742","body":"## Overview\n\nA flaw was found in the Model Context Protocol (MCP) Go SDK. When an HTTP-based MCP server is run on localhost without authentication, a malicious website can exploit a DNS rebinding vulnerability. This allows the attacker to bypass same-origin policy restrictions and send requests to the local MCP server. Consequently, an attacker could invoke tools or access resources exposed by the MCP server on behalf of the user.\n\n## Vendor advisories\n\n- **RHSA-2026:21772** · Red Hat · fixed in: Red Hat OpenShift Dev Spaces 3.28 · released 2026-05-28 · [advisory](https://access.redhat.com/errata/RHSA-2026:21772)\n- **Red Hat VEX** · Important · affected: Migration Toolkit for Virtualization, OpenShift Serverless · no fix planned: Migration Toolkit for Virtualization, OpenShift Serverless · updated 2026-10-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34742.json)\n\n**github.com/modelcontextprotocol/go-sdk: Model Context Protocol (MCP) Go SDK: DNS rebinding vulnerability allows unauthorized access** — rated Important by Red Hat. Released 2026-04-02, updated 2026-10-15.\n\nAffected:\n\n- Migration Toolkit for Virtualization\n- OpenShift Serverless\n\nFixed:\n\n- Red Hat OpenShift Dev Spaces 3.28\n\nNo fix planned:\n\n- Migration Toolkit for Virtualization\n- OpenShift Serverless\n\nNot affected:\n\n- Red Hat OpenShift Dev Spaces 3.28\n- OpenShift Lightspeed\n- Red Hat OpenShift AI (RHOAI)\n\n## Remediation\n\nBefore applying this update, make sure all previously released errata relevant to your system have been applied.\nFor details on how to apply this update, refer to:\nhttps://access.redhat.com/articles/11258 https://access.redhat.com/errata/RHSA-2026:21772\n\nWorkarounds / mitigations:\n\n- 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.\n\n## Package advisory (CVE-2026-34742)\n\nAffected packages:\n\n- `github.com/modelcontextprotocol/go-sdk < 1.4.0`\n\nPatched in:\n\n- `github.com/modelcontextprotocol/go-sdk 1.4.0`\n\nSource: https://osv.dev/vulnerability/GHSA-xw59-hvm2-8pj6","depth":"twilight","depthScore":44,"depthScoreParts":{"impact":44,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":222230,"id":"CVE-2026-34742","ts":1792065115728,"field":"cvss","old":"8.1","new":"8"}]}