![]() Now open up /etc/gdm3/nf with vi editor as follows: $ sudo vi /etc/gdm3/nfĬopy and paste the following two lines below directive. Step-1: Modify GDM conf file.īefore doing any changes take a back up: $ sudo cp /etc/gdm3/nf /etc/gdm3/ For Security reason user can’t login with root user.įor development and advanced operation, some user may prefer to login as root.įollow the steps to enable root login on Ubuntu 18.04 GDM display manager. Ubuntu 18.04 comes with GDM (Gnome Display Manager) as a default Display Manager. “And that’s the story of how the end of my workday was the start of an 0-day!” he added.How to Configure gdm3 to allow root login? Users are urged to update to the latest Ubuntu build.īackhouse released a proof-of-concept video demonstrating the exploit in action: The issue was discovered in version 20.04 and has since been fixed. The service checks how many users are on the system using the accounts-daemon, but with the daemon being out of action thanks to the previous vulnerability, the dialog box would be triggered, allowing an attacker to create a new admin profile. The second bug impacts Ubuntu’s GNOME Display Manager (gdm3), which handles user sessions and the login screen.Īs Backhouse noted, the gnome-initial-setup dialog box is usually triggered when there are no users accounts on the Ubuntu system. “No big deal: I used Ctrl-Alt-F4 to open a console, logged in (the console login was not affected by the DoS ), and killed accounts-daemon with a SIGSEGV.” Time out pam_environment symlink and had forgotten to delete it before closing the lid,” Backhouse wrote. ![]() He finished and closed his laptop lid but, when he opened it again, saw that he was locked out of his account. ![]() The two-stage exploit was discovered by GitHub security researcher Kevin Backhouse, who said he stumbled upon it at the end of a working day.īackhouse had discovered that Ubuntu desktop was vulnerable to a DoS attack, and was writing up a security report, he explained in a GitHub Security Lab blog post yesterday (November 10). When combined, the vulnerabilities allowed a malicious user to create a new administrator account without having the relevant permissions, enabling them to completely take over devices running the OS. The LPE vulnerability, which only impacts the desktop version, is the result of two bugs – a denial-of-service (DoS) vulnerability and a timeout flaw that was discovered in the user registration process. ![]() Ubuntu, the Debian-based Linux distribution, ships in three versions: desktop, server, and core for IoT devices. How an accidental discovery saw one security researcher gain complete control of Linux devicesĪ security researcher has told how he accidentally achieved local privilege escalation (LPE) on the Ubuntu operating system by chaining two vulnerabilities to gain root access. ![]()
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