Linux kernel flaw endangers millions of PCs, servers and Android devices

The vulnerability could allow malicious apps or hackers to gain root access from a limited account

For almost three years, a serious vulnerability in the Linux kernel could have allowed attackers to take full control over Linux-based PCs, servers, Android phones and other embedded devices.

The flaw, which stems from the kernel's keyring facility, allows applications running under a local user to execute code in the kernel. As a result, an attacker with access to only a limited account on a Linux system can escalate their privileges to root.

The vulnerability, tracked as CVE-2016-0728, was found and reported to the Linux kernel security team and several Linux distribution maintainers by researchers from an Israeli threat defense start-up called Perception Point.

The Linux kernel is the core of all Linux-based operating systems, including Android. Its keyring facility provides a way for applications to store sensitive information such as authentication and encryption keys inside the kernel, where other user-space applications cannot access it.

The Perception Point researchers found a way to trick the kernel into freeing a still-referenced keyring object and then to overwrite it with malicious content so it gets executed. According to them, the vulnerability was introduced in kernel version 3.8, released in Feb. 2013.

Linux distributions will release security patches for this vulnerability this week, so users should update their kernels as soon as possible. However, some systems will likely remain vulnerable for some time to come, if not indefinitely.

For example, automatic updates are not enabled on many Linux-based production servers, said Yevgeny Pats, co-founder and CEO of Perception Point. In such environments administrators sometimes have to test the updates before deploying them, which can introduce significant patching delays.

What makes this vulnerability stand out compared to other Linux kernel privilege escalation flaws is that it affects all architectures, including ARM.

This means that many embedded devices that run one of the affected kernel versions released over the past three years are also vulnerable. This includes devices running Android 4.4 (KitKat) and later, which currently account for almost 70 percent of all Android devices.

The Android ecosystem is known for its version fragmentation and long update delays. Google shares security patches with Android device manufacturers, who then have to apply them to their separately maintained source code trees and build updated firmware packages for each of their products. Some of the updates then need to be distributed to users with the help of mobile carriers.

Most Android devices receive software support for only 18 months after which they're cut off from patches. This means that a considerable number of devices will never receive a fix for this vulnerability.

The situation is not very different with consumer routers and other embedded devices that need to be manually updated by users and for which firmware patches are rare to begin with.

CPU-based protections like Supervisor Mode Access Prevention (SMAP) and Supervisor Mode Execution Protection (SMEP), or features like SELinux on Android can make exploiting this vulnerability harder, but there are ways to bypass such mitigations, Pats said.

Perception Point is not aware of any attack exploiting this vulnerability in the wild, but the company believes that computers emergency response teams and larger security vendors might be in a better position to discover if such attacks have happened.

Join the PC World newsletter!

Error: Please check your email address.

Our Back to Business guide highlights the best products for you to boost your productivity at home, on the road, at the office, or in the classroom.

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Lucian Constantin

IDG News Service
Show Comments

Essentials

Lexar® JumpDrive® S57 USB 3.0 flash drive

Learn more >

Microsoft L5V-00027 Sculpt Ergonomic Keyboard Desktop

Learn more >

Mobile

Lexar® JumpDrive® S45 USB 3.0 flash drive 

Learn more >

Exec

HD Pan/Tilt Wi-Fi Camera with Night Vision NC450

Learn more >

Audio-Technica ATH-ANC70 Noise Cancelling Headphones

Learn more >

Lexar® JumpDrive® C20c USB Type-C flash drive 

Learn more >

Lexar® Professional 1800x microSDHC™/microSDXC™ UHS-II cards 

Learn more >

Budget

Back To Business Guide

Click for more ›

Most Popular Reviews

Latest News Articles

Resources

PCW Evaluation Team

Azadeh Williams

HP OfficeJet Pro 8730

A smarter way to print for busy small business owners, combining speedy printing with scanning and copying, making it easier to produce high quality documents and images at a touch of a button.

Andrew Grant

HP OfficeJet Pro 8730

I've had a multifunction printer in the office going on 10 years now. It was a neat bit of kit back in the day -- print, copy, scan, fax -- when printing over WiFi felt a bit like magic. It’s seen better days though and an upgrade’s well overdue. This HP OfficeJet Pro 8730 looks like it ticks all the same boxes: print, copy, scan, and fax. (Really? Does anyone fax anything any more? I guess it's good to know the facility’s there, just in case.) Printing over WiFi is more-or- less standard these days.

Ed Dawson

HP OfficeJet Pro 8730

As a freelance writer who is always on the go, I like my technology to be both efficient and effective so I can do my job well. The HP OfficeJet Pro 8730 Inkjet Printer ticks all the boxes in terms of form factor, performance and user interface.

Michael Hargreaves

Windows 10 for Business / Dell XPS 13

I’d happily recommend this touchscreen laptop and Windows 10 as a great way to get serious work done at a desk or on the road.

Aysha Strobbe

Windows 10 / HP Spectre x360

Ultimately, I think the Windows 10 environment is excellent for me as it caters for so many different uses. The inclusion of the Xbox app is also great for when you need some downtime too!

Mark Escubio

Windows 10 / Lenovo Yoga 910

For me, the Xbox Play Anywhere is a great new feature as it allows you to play your current Xbox games with higher resolutions and better graphics without forking out extra cash for another copy. Although available titles are still scarce, but I’m sure it will grow in time.

Featured Content

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?