When Tony reported on the release of new VMware patches on April 4th, we didn't immediately spot that the same day there was also a release of a for-pay exploit against CVE-2009-1244 (announced in VMSA-2009-0006).

Seems a few days later, there is also a white paper available -for pay as well-, and now also a flash video of the alleged exploit showing a XP client OS exploiting a Vista host OS (launching calc.exe). The video also comments that they get a data leak back from the host to the client (hard to tell, all you see is a number of pixels being mangled on the screen).

The consequences of this are important. Virtualisation is often used just to consolidate different functions on a shared hardware, and I've seen great uses of it to e.g. be able to continue to run an accounting package that needed an OS that would not run anymore on modern hardware. I've also seen great uses where they cloned images of machines in order to let users have access to archived machines, and then remove the clone after use in order to preserve integrity of such systems.

But there are more risky uses:

• Virtualisation is also often used instead of physical separation of systems and vulnerabilities like this one and the exploits against it are a real issue one needs to address if virtualisation is goign to be used as a security measure.
  I've helped with a number of studies where such use was contemplated for highly critical assets, not just using windows and vmware, but also using nearly mainframe grade unix solutions. I always had the viewpoint that software separation is always going to be more risky than an airgap.
  But it's a hard sell as there often is no hard evidence that it can be broken (and vendors usually tell your customer it cannot). That flash video might be what one needs to stop those taking chances they ought not to take and consider the benefits vs. the risk they are taking.
• Those doing malware investigation often use virtual machines to do so as its easier to wipe them after they get infected and it's possible to run a number of them to let them communicate etc. They already face a situation where the attackers detect vmware in the malware and refuse to let it run it's course (and be studied without actually understanding the machine code). If you don't keep up to date (and even if you do - the exploit was available for sale on the same day as the patch, hence it existed earlier- that separation might still lead to exploitation of the host OS.

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Swa Frantzen -- Section 66