Nine-Year-Old Bug Found and Fixed in Sudo

Sudo is found in most Linux distributions and is responsible for elevating privileges for users, so that they can perform admin tasks. Recently it was discovered that a buffer-overflow bug ( had been in hiding for nine years. This bug (CVE-2019-18634;, which has existed in sudo versions 1.7.1 through 1.8.25p1) can be triggered when an administrator or a downstream distribution (such as any based on Debian/Ubuntu) enables the pwfeedback option in the /etc/sudoers file. Once pwfeedback is enabled, the vulnerability can be exploited by any user on the system (even those not listed in the sudoers file).

The pwfeedback option is used to hash passwords when you type them (so the irony of this feature being a security vulnerability cannot be missed).

There are two bits of good news on this front. First and foremost, the vulnerability has been patched. So long as you've updated sudo to any version beyond 1.8.25p1, you're safe. The second bit of news is that, even if you've not updated, pwfeedback isn't enabled by default in most distributions. Issue the command sudo -l to see if pwfeedback is listed among the enabled options. If not, you're good to go. If you do see pwfeedback in the output of the command, upgrade sudo immediately and consider disabling the option.

Systemd-homed Is Coming to a Linux Distribution Near You

For decades, the Linux home directories and user accounts have been managed in the same fashion. The /etc/passwd file included usernames, user IDs, and home directory locations, while the /etc/shadow file contained user password hashes. Those two files worked in conjunction to make user logins and home directories possible.

That might be changing soon, thanks to systemd-homed.

Lennart Poettering is the main developer behind the widely-adopted systemd Linux initialization system. Although much maligned initially, systemd eventually became the de facto standard for the majority of Linux distributions.

Poettering has been at work on something special for user home management.

Ladies and gentlemen, introducing systemd-homed.

Instead of using the traditional means of user/home management, systemd-homed will collect all configuration data for each component and store the information (username, group membership, password hashes, and any other relevant information) in a JSON file. On top of that, the home directories will be linked as a LUKS encrypted container, with encryption coupled with the user login. The biggest plus of this system is that as soon as a user logs in, the home directory is decrypted. Once a user logs out, the home directory is automatically encrypted.

Although this has been in development for some time, it looks like systemd-homed will officially become a reality with the release of systemd 245. That release doesn't mean all systemd-based distributions will automatically adopt systemd-homed. However the idea of on-demand home directory encryption should appeal to most distributions and users.

Original announcement:

More Online

Linux Magazine


Building a Virtual NVMe Drive * Petros Koutoupis

An economical and high-performing hybrid NVMe SSD is exported to host servers that use it as a locally attached NVMe device.

ADMIN Online

Manipulation Detection with AFICK * Tim Schürmann

AFICK is a small, free tool that helps administrators detect attempts to manipulate documents and system files.

Cron Alternatives fcron and hcron * Anzela Minosi

The fcron and hcron scheduler alternatives to cron are suitable for computers that do not run around the clock, and each comes with specific benefits.

Container IDE with Cloud Connection * Bernhard Bablok

Gitpod relies on technologies such as Docker and Eclipse Theia to serve up individual development environments for GitHub projects.

Buy this article as PDF

Express-Checkout as PDF
Price $2.95
(incl. VAT)

Buy Linux Magazine

Get it on Google Play

US / Canada

Get it on Google Play

UK / Australia

Related content

comments powered by Disqus
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters

Support Our Work

Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.

Learn More