The digitalization of our societies makes them increasingly vulnerable to emerging cyberthreats. These cyberthreats can manifest themselves in the form of organized, sophisticated, and persistent threat actors, as well as nonadversarial mistakes. Staff involved in responding to cyberthreats and handling incidents in organizations need cyber situation awareness. This paper presents a case study on what challenges members of staff involved in cybersecurity in a large, complex organization experience when developing cyber situation awareness while handling a remote code execution vulnerability in the form of Log4Shell. Two types of qualitative empirical material were used for the case study, data collected through semi-structured interviews with ten informants, and internal documentation. The empirical material was analyzed to create a timeline of events in the organization. The results show how information about the threat spread throughout the organization, the types of artifacts that served as common operational pictures, and the role played by information sharing in maintaining staff cyber situation awareness. Three major challenges to the organization were found: (i) information sharing among staff was not effortless, (ii) there was no organization-wide common operational picture established, and (iii) inaccurate information was shared. This study adds a real-world contribution to the literature on organizational handling of cyberthreats.