Cybersecurity glossary
What is zero-day?
Also known as: 0-day, zero day vulnerability
Definition
A zero-day is a vulnerability that is exploited or known to attackers before the vendor has a fix available.
Why it matters
When a patch is released, the window shifts to "n-day" exploitation of unpatched systems, which is often when attacks spread widely. Defense in depth and fast patching limit the damage.
Common questions about zero-day
See also
Sources
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