{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-34742", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-03-30T19:17:10.224Z", "datePublished": "2026-04-02T18:32:34.781Z", "dateUpdated": "2026-04-03T15:59:37.091Z"}, "containers": {"cna": {"title": "Model Context Protocol Go SDK: DNS Rebinding Protection Disabled by Default for Servers Running on Localhost", "problemTypes": [{"descriptions": [{"cweId": "CWE-1188", "lang": "en", "description": "CWE-1188: Insecure Default Initialization of Resource", "type": "CWE"}]}], "metrics": [{"cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "PASSIVE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "baseScore": 7.6, "baseSeverity": "HIGH", "vectorString": "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", "version": "4.0"}}], "references": [{"name": "https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-xw59-hvm2-8pj6", "tags": ["x_refsource_CONFIRM"], "url": "https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-xw59-hvm2-8pj6"}, {"name": "https://github.com/modelcontextprotocol/go-sdk/pull/760", "tags": ["x_refsource_MISC"], "url": "https://github.com/modelcontextprotocol/go-sdk/pull/760"}, {"name": "https://github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6d", "tags": ["x_refsource_MISC"], "url": "https://github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6d"}, {"name": "https://github.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0", "tags": ["x_refsource_MISC"], "url": "https://github.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0"}], "affected": [{"vendor": "modelcontextprotocol", "product": "go-sdk", "versions": [{"version": "< 1.4.0", "status": "affected"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-04-02T18:32:34.781Z"}, "descriptions": [{"lang": "en", "value": "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."}], "source": {"advisory": "GHSA-xw59-hvm2-8pj6", "discovery": "UNKNOWN"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-04-03T15:58:40.335119Z", "id": "CVE-2026-34742", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-04-03T15:59:37.091Z"}}]}}

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{"cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "id": "CVE-2026-34742", "lastModified": "2026-04-03T16:10:23.730", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 7.6, "baseSeverity": "HIGH", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "PASSIVE", "valueDensity": "NOT_DEFINED", "vectorString": "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", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "security-advisories@github.com", "type": "Secondary"}]}, "published": "2026-04-02T19:21:33.023", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6d"}, {"source": "security-advisories@github.com", "url": "https://github.com/modelcontextprotocol/go-sdk/pull/760"}, {"source": "security-advisories@github.com", "url": "https://github.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0"}, {"source": "security-advisories@github.com", "url": "https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-xw59-hvm2-8pj6"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Awaiting Analysis", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-1188"}], "source": "security-advisories@github.com", "type": "Primary"}]}

{"bugzilla": {"description": "github.com/modelcontextprotocol/go-sdk: Model Context Protocol (MCP) Go SDK: DNS rebinding vulnerability allows unauthorized access", "id": "2454608", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2454608"}, "csaw": false, "cvss3": {"cvss3_base_score": "8.0", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N", "status": "draft"}, "cwe": "CWE-1188", "details": ["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-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."], "mitigation": {"lang": "en:us", "value": "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."}, "name": "CVE-2026-34742", "package_state": [{"cpe": "cpe:/a:redhat:migration_toolkit_virtualization:2", "fix_state": "Affected", "package_name": "migration-toolkit-virtualization/mtv-cli-download-rhel9", "product_name": "Migration Toolkit for Virtualization"}, {"cpe": "cpe:/a:redhat:migration_toolkit_virtualization:2", "fix_state": "Affected", "package_name": "mtv-candidate/mtv-api-rhel9", "product_name": "Migration Toolkit for Virtualization"}, {"cpe": "cpe:/a:redhat:migration_toolkit_virtualization:2", "fix_state": "Affected", "package_name": "mtv-candidate/mtv-cli-download-rhel9", "product_name": "Migration Toolkit for Virtualization"}, {"cpe": "cpe:/a:redhat:migration_toolkit_virtualization:2", "fix_state": "Affected", "package_name": "mtv-candidate/mtv-controller-rhel9", "product_name": "Migration Toolkit for Virtualization"}, {"cpe": "cpe:/a:redhat:migration_toolkit_virtualization:2", "fix_state": "Affected", "package_name": "mtv-candidate/mtv-operator-bundle", "product_name": "Migration Toolkit for Virtualization"}, {"cpe": "cpe:/a:redhat:openshift_lightspeed", "fix_state": "Affected", "package_name": "openshift-lightspeed/openshift-mcp-server-rhel9", "product_name": "OpenShift Lightspeed"}, {"cpe": "cpe:/a:redhat:serverless:1", "fix_state": "Affected", "package_name": "openshift-serverless-1/kn-client-kn-rhel9", "product_name": "OpenShift Serverless"}, {"cpe": "cpe:/a:redhat:serverless:1", "fix_state": "Affected", "package_name": "openshift-serverless-1/kn-plugin-func-func-util-rhel9", "product_name": "OpenShift Serverless"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Affected", "package_name": "rhoai/odh-mod-arch-gen-ai-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_devspaces:3", "fix_state": "Affected", "package_name": "devspaces/udi-rhel9", "product_name": "Red Hat OpenShift Dev Spaces"}], "public_date": "2026-04-02T18:32:34Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-34742\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-34742\nhttps://github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6d\nhttps://github.com/modelcontextprotocol/go-sdk/pull/760\nhttps://github.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0\nhttps://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-xw59-hvm2-8pj6"], "threat_severity": "Important"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,1.4.0)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "go-sdk", "source": "cna", "vendor": "modelcontextprotocol"}, "product": "go-sdk", "vendor": "modelcontextprotocol"}], "analysis": {"en": {"generated_at": "2026-04-02T22:23:05.612738+00:00", "value": {"mitigation_remediation": ["Upgrade to Model Context Protocol Go SDK version 1.4.0 or later.", "If an upgrade is not possible, put the MCP server behind a firewall and restrict it to non\u2011localhost interfaces or require authentication.", "Enable DNS rebinding protection manually, if the SDK supports it, to re\u2011enable the default safeguard.", "Ensure that unauthenticated access to the MCP server is removed or tightly sandboxed."], "summary": {"action": "Immediate Patch", "impact": "Remote Code Execution"}, "threat_synthesis": {"affected_systems": "Affected are developers using the Model Context Protocol Go SDK. Any deployment of the SDK older than version 1.4.0 that exposes an HTTP server over localhost and does not employ authentication is vulnerable. The patch that disables the default vulnerability was introduced in release v1.4.0.", "description_and_impact": "The Model Context Protocol Go SDK omits DNS rebinding protection for HTTP\u2011based servers before version 1.4.0. When an MCP server runs on localhost without authentication, a malicious site can perform DNS rebinding to circumvent same\u2011origin policy and issue arbitrary requests to the local server. This exposure may let an attacker invoke backend tools or retrieve data exposed by the MCP server, effectively enabling remote code execution or unauthorized data access. The weakness is identified as CWE\u20111188.", "risk_and_exploitability": "The CVSS score of 7.6 signals a high severity, and while the EPSS is not available, the lack of KEV listing suggests that market damage is not yet observed. Attackers can exploit this flaw by hosting a malicious webpage that triggers DNS rebinding, especially if the victim\u2019s browser has an active session with the local MCP server. Because the server is assumed to be on localhost and unauthenticated, the attack typically requires the victim\u2019s browser to be tricked into making the rebinding request."}}}}, "created": "2026-04-03T07:31:43.887228+00:00", "updated": "2026-04-03T09:16:40.867798+00:00", "vendors": ["modelcontextprotocol", "modelcontextprotocol$PRODUCT$go-sdk"]}