Security+ Complete Practice Test 2025

A zero-day exploit is characterized by the fact that the vulnerability it targets is unknown to the software vendor or the general public at the time it is being exploited. Because the vendor is not aware of the vulnerability, there is no patch or fix available, making the exploit particularly dangerous. Attackers can leverage this unnoticed weakness to compromise systems, steal information, or disrupt services without the user's knowledge.

This lack of awareness by the vendor is what emphasizes the urgency and threat level of zero-day exploits—organizations are left exposed until a patch is eventually developed and deployed, which often takes time. Thus, the defining feature of a zero-day exploit is its status as an unpatched vulnerability that can be exploited before a remedy is made publicly available.