New 'ZombieLoad' Vulnerability Affects Intel Chips Dating Back to 2011, Apple Released Patch in macOS 10.14.5 [Updated]

Security researchers have discovered a new set of vulnerabilities that affect Intel chips dating back to 2011, including the chips that have been used in Apple devices.

As outlined by TechCrunch, "ZombieLoad," as it's being called, consists of four bugs that can allow hackers to exploit the design flaws in the chips to steal sensitive information directly from the processor.


These vulnerabilities are as serious as the Meltdown and Spectre vulnerabilities that were discovered in early 2018 and take advantage of the same speculative execution process, which is designed to speed up data processing and performance.

A white paper shared by notable security researchers (including some who worked on Spectre and Meltdown) offers details on how ZombieLoad functions. [PDF]

While programs normally only see their own data, a malicious program can exploit the fill buffers to get hold of secrets currently processed by other running programs. These secrets can be user-level secrets, such as browser history, website content, user keys, and passwords, or system-level secrets, such as disk encryption keys.

The attack does not only work on personal computers but can also be exploited in the cloud.

ZombieLoad impacts almost every Intel computer dating back to 2011, but AMD and ARM chips are not affected. A demonstration of ZombieLoad was shared on YouTube, displaying how it works to see what you're doing on your computer. While spying on web browsing is demoed, it can also be used for other purposes like stealing passwords.

There have been no reports of hackers taking advantage of the ZombieLoad vulnerabilities at this time, and Intel has released microcode for vulnerable processors. Apple addressed the vulnerability in the macOS Mojave 10.14.5 update that was released yesterday and in security patches for older versions of macOS that were also released yesterday.

Apple has released security updates in macOS Mojave 10.14.5 to protect against speculative execution vulnerabilities in Intel CPUs.
The issues addressed by these security updates do not affect Apple iOS devices or Apple Watch.
Apple previously released security updates to defend against Spectre—a series of speculative execution vulnerabilities affecting devices with ARM-based and Intel CPUs. Intel has disclosed additional Spectre vulnerabilities, called Microarchitectural Data Sampling (MDS), that apply to desktop and notebook computers with Intel CPUs, including all modern Mac computers.

An Apple support document on the ZombieLoad vulnerability provides details for "full mitigation" protection that can be enabled for customers with computers at heightened risk or that run untrusted software on their Macs.

Full mitigation requires using the Terminal app to enable additional CPU instructions and disable hyper-threading processing technology, which is available for macOS Mojave, High Sierra, and Sierra, but not on certain older machines. Apple says full mitigation could reduce performance by up to 40 percent, so most users will not want to enable it.

According to Intel, its microcode updates will have an impact on processor performance, but for the patch that Apple released in macOS Mojave 10.14.5, there was no measurable performance impact. Apple's fix prevents the exploitation of ZombieLoad vulnerabilities via JavaScript in Safari.

An Intel spokesperson told TechCrunch that most patched consumer devices could take a 3 percent performance hit at worst, and as much as 9 percent in a datacenter environment. But, the spokesperson said, it was unlikely to be noticeable in most scenarios.

As mentioned above, customers who enable Apple's full mitigation option will indeed see processor slowdowns because of the need to disable hyper-threading.

One of the researchers who discovered ZombieLoad, Daniel Gruss, told TechCrunch that ZombieLoad is easier to exploit than Spectre, but more difficult than Meltdown, and that it requires a specific set of skills, which means the average person doesn't need to worry.

Update: This article previously said that Apple would release a patch, but it has been updated to clarify that Apple addressed the issue in security updates made available to Mac owners yesterday. Customers running Mojave should update to macOS 10.14.5, while customers running older versions of macOS should install any available security updates.