{"id":"CVE-2026-44430","sourceIdentifier":"security-advisories@github.com","published":"2026-05-14T21:16:46.827","lastModified":"2026-10-26T14:10:00.130","vulnStatus":"Modified","cveTags":[],"descriptions":[{"lang":"en","value":"The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.7, the Registry's HTTP-based namespace verification (POST /v0/auth/http, POST /v0.1/auth/http) uses safeDialContext (internal/api/handlers/v0/auth/http.go:67-110) to refuse dialling private/internal addresses when fetching the well-known public-key file from a publisher-supplied domain. The blocklist (isBlockedIP, lines 125-133) relies entirely on Go stdlib's IsLoopback / IsPrivate / IsLinkLocalUnicast / IsMulticast / IsUnspecified plus a manual CGNAT range. None of these cover IPv6 6to4 (2002::/16), NAT64 (64:ff9b::/96 and 64:ff9b:1::/48 per RFC 8215), or deprecated site-local (fec0::/10) — all of which encode arbitrary IPv4 in the address bits and tunnel to RFC1918 / cloud-metadata services on dual-stack / NAT64-enabled hosts. This vulnerability is fixed in 1.7.7."},{"lang":"es","value":"El Registro MCP proporciona a los clientes MCP una lista de servidores MCP, como una tienda de aplicaciones para servidores MCP. Antes de la versión 1.7.7, la verificación de espacio de nombres basada en HTTP del Registro (POST /v0/auth/http, POST /v0.1/auth/http) utiliza safeDialContext (internal/API/handlers/v0/auth/http.go:67-110) para rechazar la marcación de direcciones privadas/internas al obtener el archivo de clave pública conocido de un dominio proporcionado por el editor. La lista de bloqueo (isBlockedIP, líneas 125-133) se basa completamente en IsLoopback / IsPrivate / IsLinkLocalUnicast / IsMulticast / IsUnspecified de la biblioteca estándar de Go, más un rango CGNAT manual. Ninguno de estos cubre IPv6 6to4 (2002::/16), NAT64 (64:ff9b::/96 y 64:ff9b:1::/48 según RFC 8215), o el obsoleto site-local (fec0::/10) - todos los cuales codifican IPv4 arbitrario en los bits de la dirección y tunelizan a servicios RFC1918 / de metadatos en la nube en hosts con doble pila / habilitados para NAT64. Esta vulnerabilidad se corrige en la versión 1.7.7."}],"affected":[{"source":"security-advisories@github.com","affectedData":[{"vendor":"modelcontextprotocol","product":"registry","versions":[{"version":"< 1.7.7","status":"affected"}]}]}],"metrics":{"cvssMetricV40":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"4.0","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/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","baseScore":6.3,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"LOW","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","confidentialityRequirement":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","availabilityRequirement":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED"}}],"cvssMetricV31":[{"source":"nvd@nist.gov","type":"Primary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N","baseScore":4.0,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"NONE","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"NONE","integrityImpact":"LOW","availabilityImpact":"NONE"},"exploitabilityScore":2.2,"impactScore":1.4}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-05-15T15:28:49.027330Z","id":"CVE-2026-44430","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"weaknesses":[{"source":"security-advisories@github.com","type":"Secondary","description":[{"lang":"en","value":"CWE-918"}]}],"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:lfprojects:mcp_registry:*:*:*:*:*:*:*:*","versionEndExcluding":"1.7.7","matchCriteriaId":"158B1594-CF93-4F53-85DE-7909E8E4B136"}]}]}],"references":[{"url":"https://github.com/modelcontextprotocol/registry/security/advisories/GHSA-r48c-v28r-pf6v","source":"security-advisories@github.com","tags":["Exploit","Vendor Advisory"]},{"url":"https://github.com/modelcontextprotocol/registry/security/advisories/GHSA-r48c-v28r-pf6v","source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","tags":["Exploit","Vendor Advisory"]}]}