Don’t miss this patch: Bad Intel drivers give hackers a backdoor to the Windows kernel

Nearly three months after infosec biz Eclypsium highlighted widespread security weaknesses in third-party Windows hardware drivers, you can now add Intel to the list of vendors leaving holes in their all-powerful low-level code.

In a follow-up report to its August DEF CON presentation, Eclypsium found that not only are those third-party kernel-mode drivers still vulnerable, widely used Intel drivers also contain many of the same holes.

As was noted in that conference talk by Jesse Michael and Mickey Shkatov, vulnerabilities in drivers are a huge risk because the code typically runs at the lowest levels in an operating system, has access to peripherals, storage, and applications, and thus if exploited, will grant miscreants total control over a machine. The drivers are also signed off by Microsoft and are therefore trusted by the operating system.

It is worth noting that these are not remotely exploitable flaws: hackers need to already be running code locally in order to get at the vulnerable drivers.

Now, Eclypsium says that it can detail three more drivers it held back of that original report, all from Intel.

Two of the vulnerable drivers were quietly patched in August by Intel. However, a third driver, Intel PMxDrv, was found to be far more difficult to clean up. On Tuesday this week, Chipzilla was finally able to release a patch, and Eclypsium was cleared to report the bug.

According to the research team, an attacker who was able to access this driver would be able to do everything from injecting code into memory to accessing I/O and PCI controllers – essentially having full reign over the machine at a very low level.

“This level of access can provide an attacker with near-omnipotent control over a victim device,” Eclypsium explains. “Just as importantly, this capability has been included as a staple component of many Intel ME and BIOS related toolsets going back to 1999.”

Users and admins are advised to download and install patched versions of the drivers as soon as possible.

Even after those Intel drivers are updated, the researchers say users will still be at risk from other drivers. One particularly dangerous example they noted was WinRing0, a component included with the OpenHardwareMonitor library. The driver is not only vulnerable to local elevation of privilege attacks, but is also commonly used by developers under more than two dozen different names.

Because the driver is trusted and so widespread, admins and users are in a race to patch the software before scumbags exploit it.

“One of the key issues noted above is that there is no universally applicable way to prevent Windows from loading any of the bad drivers that have been identified thus far,” Eclypsium notes.

There is, the researchers say, a long-term solution in the works. Microsoft is rolling out a new security tool called HVCI that will isolate drivers from the system kernel and prevent these sort of EoP attacks. Unfortunately, it will take some time to get put into place.

“HVCI requires a 7th generation or newer processor, new processor features such as mode-based execution control, and is not supported by many 3rd party drivers,” the researchers explain.

“As a result, many devices in use today will not be able to enable HVCI and will not be protected.”

In the meantime, users and admins are advised to protect themselves as best they can by avoiding software from untrusted sources and making sure their firmware and drivers are fully up-to-date and patched. ®

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