Zero-Day
A zero-day vulnerability is a security flaw unknown to the vendor, with no patch available. A zero-day exploit is a method of taking advantage of that flaw; a zero-day attack is its use against a target.
Also known as: zero-day vulnerability, 0-day
A researcher can discover and report a zero-day without anyone having attacked a system with it. The flaw, the means to exploit it, and an observed attack are separate facts. Tenable’s explanation of zero-day vulnerabilities distinguishes these stages; NIST defines a zero-day attack around exploitation of a previously unknown vulnerability.
Security reports can use different milestones when classifying exploitation, including disclosure or patch availability. State which one a report uses when comparing time to exploit. The zero-day label alone does not tell you the flaw’s severity, whether your system is affected, or whether an attack succeeded. Dan Lorenc discusses exploitation before disclosure and the pressure it puts on remediation in the episode below.
