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.
Published: 2026-05-14
Score: 6.3 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-r48c-v28r-pf6v MCP Registry has an unauthenticated SSRF: HTTP namespace verification dials 6to4 / NAT64 / site-local IPv6 addresses, bypassing private-address allowlist
History

Fri, 15 May 2026 18:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Fri, 15 May 2026 17:45:00 +0000

Type Values Removed Values Added
First Time appeared Lfprojects
Lfprojects mcp Registry
CPEs cpe:2.3:a:lfprojects:mcp_registry:*:*:*:*:*:*:*:*
Vendors & Products Lfprojects
Lfprojects mcp Registry
Metrics cvssV3_1

{'score': 4.0, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N'}

Thu, 14 May 2026 21:15:00 +0000

Type Values Removed Values Added
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.
Title MCP Registry: Unauthenticated SSRF: HTTP namespace verification dials 6to4 / NAT64 / site-local IPv6 addresses, bypassing private-address allowlist
Weaknesses CWE-918
References
Metrics cvssV4_0

{'score': 6.3, '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'}

Subscriptions

Lfprojects Mcp Registry
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-05-15T18:05:09.489Z

Reserved: 2026-05-06T14:40:00.954Z

Link: CVE-2026-44430

cve-icon Vulnrichment

Updated: 2026-05-15T15:29:05.288Z

cve-icon NVD

Status : Modified

Published: 2026-05-14T21:16:46.827

Modified: 2026-05-15T19:16:59.647

Link: CVE-2026-44430

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-14T22:30:25Z

Weaknesses