# CVE-2026-44430: MCP Registry has an unauthenticated SSRF: HTTP namespace verification dials 6to4 / NAT64 / site-local IPv6 addresses, bypassing private-address allowlist

> Attackers can bypass IP allowlists via IPv6 tunneling to access internal services or cloud metadata in the MCP Registry.

- **Severity:** Medium 6.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 May 2026
- **Updated:** 15 May 2026
- **Also known as:** GHSA-r48c-v28r-pf6v, GO-2026-5607

## What is CVE-2026-44430?

CVE-2026-44430 is a medium-severity server-side request forgery vulnerability in modelcontextprotocol registry, published on 14 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-44430?

3 open source packages ship an affected version, including github.com/modelcontextprotocol/registry. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/modelcontextprotocol/registry` | Go | All versions | 1.7.7 |
| `github.com/modelcontextprotocol/registry` | Go | All versions | 1.7.7 |
| `github.com/modelcontextprotocol/registry` | Go | All versions | 1.7.7 |

Products: Lfprojects Mcp Registry.

## How do I fix CVE-2026-44430?

Upgrade github.com/modelcontextprotocol/registry to 1.7.7 or later.

## Is CVE-2026-44430 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44430 exists.

## Other vulnerabilities in modelcontextprotocol registry

- [CVE-2026-44429](https://insights.sbomify.com/CVE-2026-44429/): MCP Registry: Stored XSS in catalogue UI via attribute-quote breakout in publisher-controlled `websiteUrl` (medium 5.1)
- [CVE-2026-44428](https://insights.sbomify.com/CVE-2026-44428/): MCP Registry: GitHub OIDC tokens replayable across registry deployments due to shared audience (low 2.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-44430 and fix it if it is affected.

What it is: CVE-2026-44430 is a medium-severity server-side request forgery vulnerability in modelcontextprotocol registry, published on 14 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44430 exists.

Affected packages and fixed versions:
- github.com/modelcontextprotocol/registry (Go): affected all versions; fixed in 1.7.7
- github.com/modelcontextprotocol/registry (Go): affected all versions; fixed in 1.7.7
- github.com/modelcontextprotocol/registry (Go): affected all versions; fixed in 1.7.7

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-44430/ (Markdown: https://insights.sbomify.com/CVE-2026-44430/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-44430
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-44430
- OSV: https://osv.dev/vulnerability/CVE-2026-44430

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-44430/
Summaries are generated and may contain mistakes; the official description above is the record.