Final answer:
To address a zero-day vulnerability, the security administrator should review the CVE database for detailed vulnerability information, consult security vendor pages for real-time alerts and solutions, and check the server's vendor documentation for advisories and secure configuration guidelines.
Step-by-step explanation:
If a new security administrator is tasked with mitigating the exposure to a zero-day vulnerability for application servers, the following three resources should be reviewed for comprehensive information. First would be the CVE database, which catalogs publicly disclosed cybersecurity vulnerabilities and exposures in a standardized way, providing detailed information about each vulnerability, its potential impacts, and possible mitigations.
Next, Security vendor pages are vital as they often contain real-time alerts and solutions for recent vulnerabilities that affect their products. These pages may also include workaround or patch information. Lastly, the server's vendor documentation may contain specific advisories and recommended actions regarding the secure configuration and patch management of the application server in question.