Critical Xen hypervisor flaw endangers virtualized environments

The vulnerability allows attackers with access to a guest OS to read the host's memory

A critical vulnerability in the widely used Xen hypervisor allows attackers to break out of a guest operating system running inside a virtual machine and access the host system's entire memory.

This is a serious violation of the security barrier enforced by the hypervisor and poses a particular threat to multi-tenant data centers where the customers' virtualized servers share the same underlying hardware.

The open-source Xen hypervisor is used by cloud computing providers and virtual private server hosting companies, as well as by security-oriented operating systems like Qubes OS.

The new vulnerability affects Xen 4.8.x, 4.7.x, 4.6.x, 4.5.x, and 4.4.x and has existed in the Xen code base for over four years. It was unintentionally introduced in December 2012 as part of a fix for a different issue.

The Xen project released a patch Tuesday that can be applied manually to vulnerable deployments. The good news is that the vulnerability can only be exploited from 64-bit paravirtualized guest operating systems.

Xen supports two types of virtual machines: Hardware Virtual Machines (HVMs), which use hardware-assisted virtualization, and paravirtualized (PV) VMs that use software-based virtualization. Based on whether they use PV VMs, Xen users might be affected or not.

For example, Amazon Web Services said in an advisory that its customers' data and instances were not affected by this vulnerability and no customer action is required. Meanwhile, virtual private server provider Linode had to reboot some of its legacy Xen servers in order to apply the fix.

Qubes OS, an operating system that uses Xen to isolate applications inside virtual machines, also put out an advisory warning that an attacker who exploits another vulnerability, for example inside a browser, can exploit this Xen issue to compromise the whole Qubes system.

The Qubes developers have released a patched Xen package for Qubes 3.1 and 3.2 and reiterated their intention to stop using paravirtualization altogether in the upcoming Qubes 4.0.

Vulnerabilities that allow breaking the isolation layer of virtual machines can be very valuable for attackers. The recent Pwn2Own hacking contest offered a $100,000 reward for virtual machine escapes in VMware Workstation or Microsoft Hyper-V. Exploit acquisition firm Zerodium offers up to $50,000 for such an exploit.

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.
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

Brand Post

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Luke Hill

MSI GT75 TITAN

I need power and lots of it. As a Front End Web developer anything less just won’t cut it which is why the MSI GT75 is an outstanding laptop for me. It’s a sleek and futuristic looking, high quality, beast that has a touch of sci-fi flare about it.

Emily Tyson

MSI GE63 Raider

If you’re looking to invest in your next work horse laptop for work or home use, you can’t go wrong with the MSI GE63.

Laura Johnston

MSI GS65 Stealth Thin

If you can afford the price tag, it is well worth the money. It out performs any other laptop I have tried for gaming, and the transportable design and incredible display also make it ideal for work.

Andrew Teoh

Brother MFC-L9570CDW Multifunction Printer

Touch screen visibility and operation was great and easy to navigate. Each menu and sub-menu was in an understandable order and category

Louise Coady

Brother MFC-L9570CDW Multifunction Printer

The printer was convenient, produced clear and vibrant images and was very easy to use

Edwina Hargreaves

WD My Cloud Home

I would recommend this device for families and small businesses who want one safe place to store all their important digital content and a way to easily share it with friends, family, business partners, or customers.

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?