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.
- 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
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
Which versions are affected by CVE-2026-45781?
3 open source packages ship an affected version, including github.com/modelcontextprotocol/registry.
| Package | 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.
Sources
Also known as GHSA-2v5f-5r6w-p67r, GO-2026-5008.