It's the Mac users' worst nightmare; a software bug that could lead to their machines being attacked by Windows. According to security researcher, a bug in VMware's Fusion virtualisation software could be used to run malicious code on a Mac by exploiting Windows in a virtual machine.
VMware has released Fusion 2.0.4 to plug the hole.
Kostya Kortchinsky, an exploit researcher at Immunity, said a critical vulnerability in VMware's virtual machine display function could be used to read and write memory on the "host" operating system - the OS running the physical hardware.
Kortchinsky crafted an exploit for Immunity's customers - the Miami-based company is best-known for its Canvas penetration testing tool - and posted a video clip that demonstrates an attack on a machine running Windows Vista Service Pack 1 (SP1) as the host operating system, and Windows XP as the "guest," the OS running in a virtual machine.
"This is indeed a guest-to-host exploit," said Kortchinsky. "It uses several vulnerabilities in the 'Display functions' (as VMware put it) that allow [someone] to read and write arbitrary memory in the host. Thus the guest can run some code on the host, effectively bypassing ASLR and DEP on Vista SP1."
The same tactics can be employed against a guest operating system - say Windows XP - running in Fusion on a Mac powered by Apple's Mac OS X, Kortchinsky confirmed. "The vulnerability is also present in VMware Fusion and as such would allow a guest (Windows or Linux) to run code on the Mac OS X host," he said. "We didn't implement this exploit though, but will probably in a near future."
The company has published a white paper discussing the VMware vulnerabilities, as well as working exploits that can compromise Windows or Ubuntu hosts; the paper and exploits, however, are available only to Canvas Early Updates customers.
VMware has issued a security advisory acknowledging the bug, and provided links to new versions of its products that patched the problem. Fusion 2.0.4, a 186MB file, can be downloaded free-of-charge from VMware's site by current users of the company's Mac virtualisation software.
Fusion, and its primary commercial competitor, Parallels Desktop, are used on a large number of Macs by users, most of whom want a virtual environment to run Windows applications. Sales of Fusion and Parallels were up 50 percent last September over the same month the year before, market research company NPD Group said then.