Zero-day vulnerability

A security flaw in software or hardware that the responsible vendor does not know about or has not fixed, leaving affected systems exposed to attack.

Exploit: Code or a technique that takes advantage of a vulnerability to cause unintended behavior. An exploit turns a zero-day flaw into a practical route for attacking vulnerable systems.
Vulnerability research: The systematic study of software and hardware weaknesses to identify and understand security flaws. Researchers are one source of discoveries that can become zero-day disclosures.
Advanced persistent threat: A sustained, targeted cyber intrusion conducted by a capable adversary seeking long-term access. Sophisticated intrusion groups may use zero-days to enter hardened targets.
Patch management: The process of acquiring, testing, and deploying software updates across systems. Rapid deployment limits exposure once a zero-day fix becomes available.
Remote code execution: An attack outcome in which an attacker runs code on a target system from a remote location. Some zero-day exploits let attackers execute commands without physical access.
Fuzzing: A testing technique that supplies many generated inputs to software to uncover crashes and other defects. Fuzzing can expose previously unknown flaws in complex programs.
Cyberwarfare: The use of cyber operations by states or their proxies to pursue political or military objectives. States may use zero-days in espionage or operations against critical systems.
Incident response: An organized process for detecting, containing, investigating, and recovering from security incidents. Organizations need response plans when exploitation precedes a patch.
Attack surface: The set of points where an attacker can attempt to enter or affect a system. A zero-day matters most where exposed interfaces make exploitation reachable.
Responsible disclosure: A process for privately reporting a vulnerability to its maintainer and coordinating publication and remediation. Coordinated reporting can shorten the period between discovery and a fix.

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