Cryptsetup Vulnerability Grants Root Shell Access On Some Linux Systems

msm1267 quotes a report from Threatpost: A vulnerability in cryptsetup, a utility used to set up encrypted filesystems on Linux distributions, could allow an attacker to retrieve a root rescue shell on some systems. From there, an attacker could have the ability to copy, modify, or destroy a hard disk, or use the network to exfiltrate data. Cryptsetup, a utility used to setup disk encryption based on the dm-crypt kernel module, is usually deployed in Debian and Ubuntu. Researchers warned late last week that if anyone uses the tool to encrypt system partitions for the operating systems, they’re likely vulnerable. Two researchers, Hector Marco of the University of the West of Scotland and Ismael Ripoll, of the Polytechnic University of Valencia, in Spain, disclosed the vulnerability on Friday at DeepSec, a security conference held at the Imperial Riding School Renaissance Vienna Hotel in Austria. According to a post published to the Full Disclosure mailing list, the vulnerability (CVE-2016-4484) affects packages 2.1 and earlier. Systems that use Dracut, an infrastructure commonly deployed on Fedora in lieu of initramfs — a simple RAM file system directory, are also vulnerable, according to the researchers. The pair say additional Linux distributions outside of Debian and Ubuntu may be vulnerable, they just haven’t tested them yet. The report adds: “The problem stems from the incorrect handling of a password check when a partition is ciphered with LUKS, or Linux Unified Key Setup, a disk encryption specification that’s standard for Linux. Assuming an attacker has access to the computer’s console, when presented with the LUKS password prompt, they could exploit the vulnerability simply by pressing ‘Enter’ over and over again until a shell appears. The researchers say the exploit could take as few as 70 seconds. After a user exceeds the maximum number of three password tries, the boot sequence continues normally. Another script in the utility doesn’t realize this, and drops a BusyBox shell. After carrying out the exploit, the attacker could obtain a root initramfs, or rescue shell. Since the shell can be executed in the initrd, or initial ram disk, environment, it can lead to a handful of scary outcomes, including elevation of privilege, information disclosure, or denial of service.”

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