The vulnerability lies in Feast's handling of the user_defined_function.body field in an OnDemandFeatureView specification. The field is base64 decoded and directly deserialized using dill.loads() before any authorization verification, allowing an attacker to craft a malicious serialized Python object containing an arbitrary __reduce__ method. Successful exploitation results in arbitrary OS command execution under the feast service account, compromising confidentiality, integrity, and availability of all data processed by the registry server.

Feast versions prior to 0.63.0 are affected. This includes all deployments of the feast registry server that expose the ApplyFeatureView gRPC endpoint, across all operating environments where Feast 0.63.0 or earlier is installed.

The CVSS score of 9.3 signifies critical severity. Although EPSS is not available, the lack of an authentication check and direct remote code execution capability imply a high likelihood of exploitation in environments where the gRPC interface is reachable from untrusted networks. The vulnerability is not listed in the CISA KEV catalog, but the attack surface remains significant for any publicly exposed Feast registry.