The CVE-2016-4484 vulnerability can be exploited to gain a Linux Root shell by simply pressing the Enter Key for 70 Seconds.
It could be quite easy to bypass the authentication procedures on some Linux systems just by holding down the Enter key for around 70 seconds. In this way, it is possible to open a shell with root privileges and gain complete remote control over encrypted Linux machine.The problem is related to a security vulnerability, tracked as CVE-2016-4484, in the implementation of the Cryptsetup utility.
The CVE-2016-4484 was discovered by the Spanish security researchers Hector Marco and Ismael Ripoll. The principal Linux distributions, including Debian, Ubuntu, Fedora, Red Hat Enterprise Linux (RHEL), and SUSE Linux Enterprise Server (SLES) are vulnerable. Millions of users are at risk.
"A vulnerability in Cryptsetup, concretely in the scripts that unlock the system partition when the partition is ciphered using LUKS (Linux Unified Key Setup). The disclosure of this vulnerability was presented as part of our talk "Abusing LUKS to Hack the System" in the DeepSec 2016 security conference, Vienna." Wrote the researchers in a security advisory.
The Cryptsetup is a utility used to conveniently setup disk encryption based on the DMCrypt kernel module.These include plain dm-crypt volumes, LUKS volumes, loop-AES and TrueCrypt (including VeraCrypt extension) format.
The bug affects the way the Cryptsetup utility handles decryption password process when a system boots up, which lets a user retry the password multiple times.
Even if the user has exhausted all 93 password attempts, the user displays a shell that has root privileges.
The experts highlighted the fact that anyway the attacker is not able to access to to the contents of the encrypted drive.
In order to fix the problem, you need to check for the availability of a patch. In case there is no patch, the problem could be solved by modifying the cryptroot file to limit the number of password attempts and stop the boot sequence when this number is reached.