As much as I know ther is no possiblity of hardware wallet being hacked as you need to deal with a physical device here.
Just because you are dealing with a physical device, this does not mean it is unhackable.
New vulnerabilities can always be found and exploited. Nothing is guaranteed to be 100% safe and secure.
A vulnerability inside the ledger architecture has been found which allowed an attacker to replace the firmware with a malicous version.
This has been fixed. And it could not lead to via the internet. Physical access prior someone using the nano s is necessary for this attack.
I think the biggest vulnerablilty for hard wallets was the connectivity requirements to smartphones.
Hardware wallets are not required to be connected to smartphones (some allow you to pair them with a mobile wallet).
And even if they would require such a connection, this would not pose any security threat. This is simply due to the fact that the private keys are generated and stored inside the hardware wallet.
They won't ever leave the device. Transactions are being sent from the mobile to the hardware wallet (an attacker might be able to insert a malicious TX here), then signed on the device after approving it via pressing the physical buttons. If you are checking the transaction on the nano s screen and only approve correct transactions, there is no other way of stealing coins in such a scenario.