modelcontextprotocol registry up to 1.7.6 /v0/auth/http server-side request forgery

Summaryinfo

A vulnerability was found in modelcontextprotocol registry up to 1.7.6 and classified as critical. The affected element is an unknown function of the file /v0/auth/http. Executing a manipulation can lead to server-side request forgery. This vulnerability appears as CVE-2026-44430. The attack may be performed from remote. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability has been found in modelcontextprotocol registry up to 1.7.6 and classified as critical. This vulnerability affects an unknown code of the file /v0/auth/http. The manipulation with an unknown input leads to a server-side request forgery vulnerability. The CWE definition for the vulnerability is CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability was named CVE-2026-44430 since 05/06/2026. The exploitation appears to be easy. The attack can be initiated remotely. Technical details are known, but there is no available exploit.

Upgrading to version 1.7.7 eliminates this vulnerability.

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Productinfo

Vendor

• modelcontextprotocol

Name

• registry

Version

• 1.7.0
• 1.7.1
• 1.7.2
• 1.7.3
• 1.7.4
• 1.7.5
• 1.7.6

Website

• Product: https://github.com/modelcontextprotocol/registry/

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