The key fob sends out a code which the car interprets to unlock the doors. Typically these codes are randomized to prevent hackers from reusing a previous code, but Subaru's implementation is flawed.

"An attacker can 'clone' the key fob, unlock cars and, when increasing the rolling code with a sufficiently high value, effectively render the user's key fob unusable," Wimmenhove wrote.

October 18, 2017 [tomwimmenhove] has found a vulnerability in the cryptographic algorithm that is used by certain Subaru key fobs and he has open-sourced the software that drives this exploit.

Tom Wimmenhove, a Dutch electronics designer, has discovered a flaw in the key fob system used by several Subaru models, a vulnerability the vendor has not patched and could be abused to hijack cars.