KEV stands for Known Exploited Vulnerabilities, a catalog of vulnerabilities that have been confirmed as used in real-world attacks. Unlike a generic vulnerability list, a KEV entry signals that defenders should treat the flaw as actively dangerous, not just theoretically severe.
KEV matters because it helps security teams prioritize limited time and patching resources. In practice, defenders use KEV data to focus on systems that are exposed, internet-facing, or contain sensitive data, especially when asset inventories are incomplete. Attackers often move quickly after disclosure, so a vulnerability that appears in KEV can indicate fast-moving exploitation, automated scanning, or mass targeting. On the defense side, KEV feeds support risk-based patching, compensating controls, and temporary mitigations when immediate remediation is not possible.