# CVE-2026-45781: MCP Registry: OCI ownership validation fails open on upstream rate limits, allowing attacker-controlled package claims

> Attackers can bypass OCI ownership validation during rate limits to claim unauthorized package namespaces in the MCP Registry.

- **Severity:** Low 3.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 14 May 2026
- **Updated:** 16 May 2026
- **Also known as:** GHSA-2v5f-5r6w-p67r, GO-2026-5008

## What is CVE-2026-45781?

CVE-2026-45781 is a low-severity vulnerability in modelcontextprotocol registry, published on 14 May 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.9, OCI ownership validation skips label-match check when upstream OCI registry returns HTTP 429, letting any authenticated publisher bind their io.github.<user>/* namespace to OCI images they do not control. internal/validators/registries/oci.go:104-119 fails open on http.StatusTooManyRequests: when the registry's anonymous fetch to the upstream OCI registry is rate-limited, ValidateOCI returns nil and the publish is accepted without ever running the io.modelcontextprotocol.server.name label-match check at lines 122-141. That label check is the only cross-system ownership proof the registry applies to OCI packages — every other registry type (NPM, PyPI, NuGet, MCPB) treats a non-200 upstream response as a hard error. This vulnerability is fixed in 1.7.9.

Weakness: CWE-636 (Not Failing Securely)

## Which versions are affected by CVE-2026-45781?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/modelcontextprotocol/registry` | Go | All versions | 1.7.9 |
| `github.com/modelcontextprotocol/registry` | Go | All versions | 1.7.9 |
| `github.com/modelcontextprotocol/registry` | Go | All versions | 1.7.9 |

## How do I fix CVE-2026-45781?

Upgrade github.com/modelcontextprotocol/registry to 1.7.9 or later.

## Is CVE-2026-45781 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-45781 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45781 and fix it if it is affected.

What it is: CVE-2026-45781 is a low-severity vulnerability in modelcontextprotocol registry, published on 14 May 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-45781 exists.

Affected packages and fixed versions:
- github.com/modelcontextprotocol/registry (Go): affected all versions; fixed in 1.7.9
- github.com/modelcontextprotocol/registry (Go): affected all versions; fixed in 1.7.9
- github.com/modelcontextprotocol/registry (Go): affected all versions; fixed in 1.7.9

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-2026-45781/ (Markdown: https://insights.sbomify.com/CVE-2026-45781/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45781
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45781
- OSV: https://osv.dev/vulnerability/CVE-2026-45781

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-45781/
Summaries are generated and may contain mistakes; the official description above is the record.