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Security bug in Xen may have exposed Amazon, other cloud services [Updated]

  • 2 October 2014
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Jasper_The_Rasper
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Flaw in hypervisor could let malicious VM read data from or crash other servers.

by Sean Gallagher - Oct 1 2014
 
The Xen Project has published a security advisory that could affect millions of virtualized servers running in Amazon’s cloud and other public hosting services. A flaw in the Xen hypervisor could allow a malicious fully virtualized server to read data about other virtualized systems running on the same physical hardware or the hypervisor hosting the virtual machine. The malicious system could also potentially crash the server hosting the virtual machines. A patch, which was privately disclosed last week under embargo, has been issued to correct the issue.
Xen is used by a number of public and private cloud providers to support infrastructure-as-a-service (IaaS) offerings such as Amazon’s Elastic Compute Cloud, Rackspace, and some configurations of the OpenStack cloud provisioning environment. The flaw, discovered by Jan Beulich at SUSE, affects servers configured to support hardware-assisted virtualization (HVM) mode virtualization. HVM lets operating systems use hardware extensions that give them faster access to the physical server’s hardware, and it uses software emulation of other Intel platform hardware to allow those operating systems to run without modification. Windows virtual machines running on Xen require HVM support.
 
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Jasper_The_Rasper
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By Chris Duckett October 1, 2014
 
A memory reading issue in Xen 4.1 and above has been publicly disclosed, along with a patch. Xen has unveiled the details of a security issue in its hypervisor that forced cloud providers Amazon and Rackspace into a full reboot of all users' affected machines over the past week.
The issue, CVE-2014-7188 / XSA-108, allowed hardware virtual machine guests to potentially read data from either other guest machines, or the hypervisor itself, Xen said in its advisory. The memory bug hit x86 systems with machines with ARM chips escaping the issue.
"The MSR [model-specific register] range specified for APIC use in the x2APIC access model spans 256 MSRs. Hypervisor code emulating read and write accesses to these MSRs erroneously covered 1,024 MSRs," Xen said.
 
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Sysadmins say less patchwork required in the cloud than own bit barns

By Simon Sharwood, 10 Oct 2014  The Xen bug that forced AWS, Rackspace and SoftLayer, among others, to reboot many of their servers appears to have gone off without a hitch, although Amazon customers report less downtime than other cloud users.
So says cloud groomer Rightscale, which asked 449 folks how the cloud reboot went for them. Here's the headline findings.
 
http://regmedia.co.uk/2014/10/10/xen_reboot_impact.png
 
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Thank Heavens a patch was issued on this bug. At least we have researchers out there keeping a eye on this malicious attack.

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