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

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.

Source published

14 May 2026 21:00:49 UTC

Source modified

16 May 2026 01:06:38 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 3.1 · 3.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N