How is a zero-day vulnerability characterized?

A zero-day vulnerability is characterized as a security flaw that has been exploited before a fix has been made available. This means that when an attacker discovers and takes advantage of this vulnerability, the software vendor is not yet aware of the issue, nor have they released a patch or solution to address it. The term "zero-day" derives from the fact that the developers have had zero days to fix the flaw since it was discovered by the attackers.

In this context, a zero-day vulnerability poses a significant risk, as it can be targeted by malicious actors, leaving users and organizations exposed until the vendor creates and deploys a patch. Understanding the implications of zero-day vulnerabilities is crucial in cybersecurity, as they can result in severe data breaches or system compromises before any defensive measures are implemented.