Zero-day attack

nounverified·updated May 9, 2026

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An attack on a piece of software that has a vulnerability for which there is no known patch.

MWEFederal Financial Institutions Examination Council (FFIEC) IT Examination Handbook Infobase, Glossary

Senses

1 more sense beyond the canonical

SANS Glossary of Security Terms

A zero-day (or zero-hour or day zero) attack or threat is a computer threat that tries to exploit computer application vulnerabilities that are unknown to others or undisclosed to the software developer. Zero-day exploits (actual code that can use a security hole to carry out an attack) are used or shared by attackers before the software developer knows about the vulnerability.

Classifications

per-axis with provenance

Entity Type

Vulnerability95%rule-basedr:entity.vulnerability.cve.v1

?unassignedlast reviewed —

Sensitivity

unclassified

Information Class

unclassified

Variants

3 surface forms

plural: Zero-day attacks
possessive: Zero-day attack's
pluralpossessive: Zero-day attacks'

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