In cybersecurity and computer science, the term “zero-day” is commonly related to troubles, threats, and hazards due to the lack of knowledge, experience, or misunderstanding. A zero-day attack is generally considered a new vulnerability with no defense; thus, the possible attack will have a highrisk probability, and a critical impact. Unfortunately, only a few surveys on the topic are available that would help understand these threats, which are not enough to construct new solutions to detect, prevent, and mitigate them. In this paper, it is conducted a review of the zero-day attack, how to understand its real impact, and a few different accessible solutions nowadays. This study introduces a useful reference that provides researchers with knowledge to understand the current problem concerning zero- days attacks; hence they could develop solutions for facing them
