Xen's highly critical virtual machine escape flaw gets a fix

It's possibly the worst flaw ever found in the Xen hypervisor, researchers say

The Xen Project fixed several vulnerabilities in its popular virtualization software, including one that could allow potential attackers to break out of a virtual machine and gain control over the host system.

Vulnerabilities that break the isolation layer between virtual machines are the most serious type for a hypervisor like Xen, whose main goal is to allow running multiple VMs on the same hardware in a secure manner.

The Xen patches released Thursday fix a total of nine vulnerabilities, but the privilege escalation one identified as CVE-2015-7835 is the most serious one.

It stems not from a traditional programming error, but from a logic flaw in how Xen implements memory virtualization for PV (paravirtualized) VMs. PV is a technique that enables virtualization on CPUs that don't support hardware-assisted virtualization.

As such, the flaw can only be exploited by malicious administrators of PV guests and only on x86 systems, the Xen Project said in an advisory. Xen versions 3.4 and higher are vulnerable.

The vulnerability, which has existed for 7 years, is "probably the worst we have seen affecting the Xen hypervisor, ever," the security team of the Qubes OS Project said in its own advisory. Qubes OS relies on Xen to compartmentalize different tasks performed by users for increased security.

"It is really shocking that such a bug has been lurking in the core of the hypervisor for so many years," the Qubes security team said. "In our opinion the Xen project should rethink their coding guidelines and try to come up with practices and perhaps additional mechanisms that would not let similar flaws to plague the hypervisor ever again (assert-like mechanisms perhaps?). Otherwise the whole project makes no sense, at least to those who would like to use Xen for security-sensitive work."

Join the Good Gear Guide 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

Microsoft L5V-00027 Sculpt Ergonomic Keyboard Desktop

Learn more >

Lexar® JumpDrive® S57 USB 3.0 flash drive

Learn more >

Mobile

Lexar® JumpDrive® S45 USB 3.0 flash drive 

Learn more >

Exec

Lexar® JumpDrive® C20c USB Type-C flash drive 

Learn more >

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

Learn more >

Audio-Technica ATH-ANC70 Noise Cancelling Headphones

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

Michael Hargreaves

Windows 10 for Business / Dell XPS

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

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

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.

Kathy Cassidy

STYLISTIC Q702

First impression on unpacking the Q702 test unit was the solid feel and clean, minimalist styling.

Anthony Grifoni

STYLISTIC Q572

For work use, Microsoft Word and Excel programs pre-installed on the device are adequate for preparing short documents.

Featured Content

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?