Vulnerability 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 Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Lfprojects | Mcp Registry | < 1.7.7 |
Related Weaknesses (CWE)
References
- https://github.com/modelcontextprotocol/registry/security/advisories/GHSA-r48c-vExploitVendor Advisory
- https://github.com/modelcontextprotocol/registry/security/advisories/GHSA-r48c-vExploitVendor Advisory
FAQ
What is CVE-2026-44430?
CVE-2026-44430 is a vulnerability with a CVSS score of 4.0 (MEDIUM). 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/au...
How severe is CVE-2026-44430?
CVE-2026-44430 has been rated MEDIUM with a CVSS base score of 4.0/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-44430?
Check the references section above for vendor advisories and patch information. Affected products include: Lfprojects Mcp Registry.