New ESX(i) 3.5 security patch released; scenarios and installation notes

April 11th, 2009 by jason Leave a reply »

On Friday April 10th, VMware released two patches:

Both address the same issue:

A critical vulnerability in the virtual machine display function might allow a guest operating system to run code on the host. The Common Vulnerabilities and Exposures Project (cve.mitre.org) has assigned the name CVE-2009-1244 to this issue.

Hackers must love vulnerabilities like this because they can get a lot of mileage out of essentially a single attack. The ability to execute code on an ESX host can impact all running VMs on that host.

Although proper virtualization promises isolation, the reality is that no hardware or software vendor is perfect and from time to time we’re going to see issues like this. Products are under constant attack from hackers (both good and bad) to find exploits. In virtualized environments, it’s important to remember that guest VMs and guest operating systems are no different than their physical counterparts in that they need to be properly protected from the network. That means adequate virus protection, spyware protection, firewalls, encryption, packet filtering, etc.

This vulnerability in VMware ESX and ESXi is really a two factor attack. In order to compromise the ESX or ESXi host, the guest VM must first be vulnerable to compromise on the network to provide the entry point to the host. Once the guest VM is compromised, the next step is to get from the guest VM to the ESX(i) host. Hosts without the patch will be vulnerable to the next attack which we know from reading above will allow who knows what code to be executed on the host. If the host is patched, we maintain our guest isolation and the attack stops at the VM level. Unfortunately, the OS running in the guest VM is still compromised, again highlighting the need for adequate protection of the operating system and applications running in each VM.

The bottom line is this is an important update for your infrastructure. If your ESX or ESXi hosts are vulnerable, you’ll want to get this one tested and implemented as soon as possible.

I installed the updates today in the lab and discovered something interesting that is actually outlined in both of the KB articles above:

  • The ESXi version of the update requires a reboot. Using Update Manager, the patch process goes like this: Remediate -> Maintenance Mode -> VMotion VMs off -> Patch -> Reboot -> Exit Maintenance Mode. The duration of installation of the patch until exiting maintenance mode (including the reboot in between) took 12 minutes.
  • The ESX version of the update does not require a reboot. Using Update Manager, the patch process goes like this: Remediate -> Maintenance Mode -> VMotion VMs off -> Patch -> Exit Maintenance Mode. The duration of installation of the patch until exiting maintenance mode (with no reboot in between) took 1.5 minutes.

Given reboot times of the host, patching ESX hosts goes much quicker than patching ESXi hosts. Reboot times on HP Proliant servers aren’t too bad but I’ve been working with some powerful IBM servers lately and the reboot times on those are significantly longer than HP. Hopefully we’re not rebooting ESX hosts on a regular basis so with that in mind, reboot times aren’t a huge concern, but if you’ve got a large environment with a lot of hosts requiring reboots, the reboot times are going to be cumulative in most cases. Consider my environment above. A 6 node ESXi cluster is going to take 72 minutes to patch, not including VMotions. A 6 node ESX cluster is going to take 9 minutes to patch, not including VMotions. This may be something to really think about when weighing the decision of ESX versus ESXi for your environment.

Update: One more item critical to note is that although the ESX version of the patch requires no reboot, the patch does require three other patches to be installed, at least one of which requires a reboot.  If you already meet the requirements, no reboot will be required for ESX to install the new patch.

In closing, while we are on the subject of performing a lot of VMotions, take a look at a guest blog post from Simon Long called VMotion Performance. Simon shows us how to modify VirtualCenter (vCenter Server) to allow more simultaneous VMotions which will significantly cut down the amount of time spent patching ESX hosts in a cluster.

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  1. Allen says:

    One thing to add to the list of things to consider in the ESX vs. ESXi debate is that while this particular patch requires a reboot with ESXi, I’ve found that patching ESXi in generall is waaaay faster than ESX (when using Update Manager anyway). For example, going from U3 to U4 is so much faster on ESXi as it is just a couple of “firmware” updates and a reboot and you are all done. On ESX, there are several patchs to install (26 of them I believe) before that reboot. We generally stick to only patching with the major updates unless a critical security patch (like this one) comes out. So in the long run, ESXi may patch faster for us. Note that we only use ESXi in the lab right now to get some exposure to it prior to maybe using it full-time with vSphere. We shall see soon enough…

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