🛡️ CVE-2026-44430
🟡 CVSS 4.0 — Medium ✅ No Known Exploit CWE-918 NVD
4.0
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

Details

Severity Medium
CVSS Score 4.0
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
CWE CWE-918
Public Exploit ✅ No
Source NVD
Published 2026-05-08
Updated 2026-06-02
Modified 2026-05-16
Fix URL N/A

Affected Packages

Software From version Fixed in
github.com/modelcontextprotocol/registry — —
mcp-registry — 1.7.7
unknown — —

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