{"cve":"CVE-2026-44430","nvd":{"published":"2026-05-14T21:16:46.827","modified":"2026-10-26T14:10:00.130","status":"Modified","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.","cvss_v4":{"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","score":6.3},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N","score":4.0},"cwes":["CWE-918"],"references":["https://github.com/modelcontextprotocol/registry/security/advisories/GHSA-r48c-v28r-pf6v","https://github.com/modelcontextprotocol/registry/security/advisories/GHSA-r48c-v28r-pf6v"],"products":["lfprojects:mcp_registry"],"source":"nvd","synced_at":"2026-10-26T14:27:29.784594657+00:00"},"epss":{"cve":"CVE-2026-44430","score":0.00285,"percentile":0.20809,"date":"2026-10-26"},"kev":null,"osv":[{"id":"GHSA-r48c-v28r-pf6v","url":"https://osv.dev/vulnerability/GHSA-r48c-v28r-pf6v","summary":"MCP Registry has an unauthenticated SSRF: HTTP namespace verification dials 6to4 / NAT64 / site-local IPv6 addresses, bypassing private-address allowlist","modified":"2026-09-10T03:51:06.901594663Z","packages":[{"ecosystem":"Go","name":"github.com/modelcontextprotocol/registry","purl":"pkg:golang/github.com/modelcontextprotocol/registry","ranges":["<1.7.7"],"fixed":["1.7.7"]}]},{"id":"GO-2026-5607","url":"https://osv.dev/vulnerability/GO-2026-5607","summary":"MCP Registry has an unauthenticated SSRF: HTTP namespace verification dials 6to4 / NAT64 / site-local IPv6 addresses, bypassing private-address allowlist in github.com/modelcontextprotocol/registry","modified":"2026-06-25T23:01:24.328460057Z","packages":[{"ecosystem":"Go","name":"github.com/modelcontextprotocol/registry","purl":"pkg:golang/github.com/modelcontextprotocol/registry","ranges":["<1.7.7"],"fixed":["1.7.7"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}