In ITIL 4, the service owner is typically the person responsible for managing a specific service throughout its lifecycle. The service owner has a deep understanding of the service's architecture, including how the components are configured and how they interact. When a vendor bulletin describes a critical issue affecting servers that play an essential role in the delivery of a service, it is the service owner who is most likely to assess how this issue could impact the organization's operations. They have the expertise to understand the dependencies of these components within the service and make informed decisions about risk mitigation and necessary actions.