The CISA Known Exploited Vulnerabilities Catalog is a U.S. government list of vulnerabilities that CISA believes are being actively exploited in the wild. It is not a full vulnerability database; it is a prioritization tool for defenders who need to decide what to patch first.
Its value is practical: when a flaw appears in the catalog, security teams should treat it as urgent, especially if the affected system is internet-facing or sits in a critical path such as a proxy, VPN, or web tier. Attackers often target these weaknesses because they are known, reachable, and sometimes unpatched. Defenders use the catalog to drive emergency patching, asset inventory, exposure reduction, and verification that fixes were applied. In modern operations, inclusion in the catalog often means the vulnerability has moved from theoretical risk to immediate defensive action.