Imagine your computer's memory as a chalkboard, where a teacher keeps track of your grades in real time. You don't allow students to use either chalk or erasers, so they can't change their grades. The "Copy Fail" vulnerability is like a sneaky student who somehow gains access to an eraser and chalk, and he changes just his grade while you're not looking.

Essentially, Copy Fail is a flaw in the Linux system responsible for handling the security of certain types of data. The flaw allows an attacker with basic access to a system to alter a crucial piece of data in the computer's RAM. Once the change is made, the altered data can trick the system into thinking that the attacker is the root user, granting the attacker full control of the system.

Think of it this way: A janitor takes the nameplate from the boss's office and slaps it on the wall beside his closet so everyone thinks he is the boss.