{"schemaVersion":3,"id":"CVE-2026-44430","aliases":["CGA-2vf3-r7jx-gq7c","CGA-4j43-mfxq-66w7","GHSA-r48c-v28r-pf6v","GO-2026-5607"],"status":"published","duplicateOf":null,"title":null,"description":"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.","dates":{"published":"2026-05-14T21:02:40.738Z","modified":"2026-05-15T18:05:09.489Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":6.3,"severity":"medium","version":"4.0","versionLabel":"v4.0","source":"CVE.org","vector":"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","computed":false,"selection":"backend-summary"},"metrics":[{"version":"4.0","versionLabel":"v4.0","source":"CVE.org","score":6.3,"severity":"medium","vector":"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","exploitability":null,"impact":null,"computed":false},{"version":"4.0","versionLabel":"v4.0","source":"OSV · Wolfi","score":6.3,"severity":"medium","vector":"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","exploitability":null,"impact":null,"computed":true},{"version":"4.0","versionLabel":"v4.0","source":"OSV · 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