The finding that would most likely indicate a high risk in a vulnerability assessment report is end of life system detected. A vulnerability assessment is a process of identifying, analyzing, and prioritizing the vulnerabilities in a system, network, or application. A vulnerability assessment report is a document that summarizes the results and findings of the vulnerability assessment, such as the number, type, severity, and impact of the vulnerabilities, as well as the recommendations and remediation actions. End of life system detected is a finding that indicates that a system, network, or application has reached the end of its life cycle, which means that it is no longer supported, maintained, or updated by the vendor or developer. End of life system detected is a high-risk finding, because it means that the system, network, or application may have unpatched or unknown vulnerabilities, which can be exploited by attackers to compromise the security, functionality, or performance of the system, network, or application. End of life system detected also means that the system, network, or application may not be compatible or compliant with the current standards, regulations, or requirements, which can cause operational, legal, or reputational issues for the organization.
References: CISSP All-in-One Exam Guide, Eighth Edition, Chapter 6: Security Assessment and Testing, page 281; [Official (ISC)2 CISSP CBK Reference, Fifth Edition, Chapter 6: Security Assessment and Testing, page 407]