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Xen Hypervisor Flaws Force Amazon, Rackspace to Reboot Servers

Rackspace, Amazon, Linode and likely other cloud providers will reboot some of their servers over the next week after they patch several vulnerabilities affecting the Xen open-source hypervisor.

Rackspace, Amazon, Linode and likely other cloud providers will reboot some of their servers over the next week after they patch several vulnerabilities affecting the Xen open-source hypervisor.

The Xen Project will disclose the details of several security holes on March 10. Cloud providers that use the software will need to fix the vulnerabilities by then.Xen vulnerabilities

Amazon says the majority of its EC2 fleet relies on newer hardware and the issues will be addressed through live updates without the need for a reboot. However, roughly 10% of EC2 instances are running on older hardware and they will need to be rebooted in order to complete the update process.

Amazon customers can log into their EC2 consoles and check the Events page to see if any of their instances are scheduled for a reboot.

“Each instance will return to normal operation after the reboot, and all instance configuration and data will be retained. If you have startup procedures that aren’t automated during your instance boot process, please remember that you will need to log in and run them. We will need to do this maintenance update in the window specified. You will not be able to stop/start or re-launch instances in order to avoid this maintenance update,” Amazon said in a security maintenance notice.

Rackspace says the Xen vulnerabilities affect its First and Next Generation Cloud Servers fleet. Rackspace customers can check their cloud control panel for additional information on the per-instance reboot windows.

“While we do everything we can to minimize service interruptions, the security of your environment is our highest priority. We understand that any downtime impacts your business and we do not make this decision lightly. In preparation for a potential reboot, we recommend that you take proactive steps to ensure your environment is configured to return to proper operations,” Rackspace said.

Linode is rebooting host servers between March 2 and March 9. The company is sending out emails to affected users and a per-Linode maintenance schedule has been made available in the Linode Manager.

Linode says a two-hour window has been allocated for each instance, but the actual downtime can be much less.

The Xen Project has already released patches for three denial-of-service (DoS) vulnerabilities reported earlier this year.

This isn’t the first time cloud providers were forced to reboot servers due to Xen vulnerabilities. Back in October, companies applied a patch to prevent malicious actors from exploiting a flaw that allowed virtualized server owners to read data from other systems on the host server.

At the time, Rackspace apologized to the roughly 50,000 affected customers after some of the reboots took longer than they should have.

Written By

Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.

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