In computer security, the word vulnerability refers to a 
weakness in a system allowing an attacker to violate the 
confidentiality, integrity, availability [i.e (C.I.A) 
NSTISSC's triangle], access control, consistency or audit 
mechanisms of the system or the data and applications it 
hosts. Vulnerabilities may result from bugs or design flaws 
in the system. A vulnerability can exist either only in 
theory, or could have a known exploit. Vulnerabilities are 
of significant interest when the program containing the 
vulnerability operates with special privileges, performs 
authentication or provides easy access to user data or 
facilities (such as a network server or RDBMS).