SSRF in Lfprojects Mcp Registry
CVE-2026-44430
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.
Vulnerability class: SSRF (Server-Side Request Forgery)
EPSS: 0.003 (20.6th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 4.0 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N.
Affected products
- Lfprojects Mcp_registry
- Modelcontextprotocol Registry — versions < 1.7.7
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-44430?
- CVE-2026-44430 is a medium-severity vulnerability in Lfprojects Mcp Registry, classified under Server-Side Request Forgery (SSRF). CVSS score: 4.0/10. Published 2026-05-14.
- How severe is CVE-2026-44430?
- Medium severity. CVSS v3 base score is 4.0 out of 10.