Chrome OS version 75, which Google released on Wednesday in the stable channel, adds more mitigations for recently disclosed Microarchitectural Data Sampling (MDS) vulnerabilities affecting most Intel processors made in the last decade.
The researchers who discovered the security holes have named them ZombieLoad, RIDL (Rogue In-Flight Data Load), Fallout, and Store-to-Leak Forwarding. Intel has assigned them the following names and CVEs: Microarchitectural Store Buffer Data Sampling (MSBDS, CVE-2018-12126), Microarchitectural Fill Buffer Data Sampling (MFBDS, CVE-2018-12130), Microarchitectural Load Port Data Sampling (MLPDS, CVE-2018-12127), and Microarchitectural Data Sampling Uncacheable Memory (MDSUM, CVE-2018-11091).
When the existence of the flaws came to light, Google informed Chrome OS users that version 74 had disabled Hyper-Threading by default, which should prevent exploitation. Chrome OS 75 includes other, unspecified mitigations for these attacks.
Google pointed out when the vulnerabilities were disclosed that disabling Hyper-Threading could have a negative impact on performance in some cases.
“Users concerned about the performance loss, such as those running CPU intensive workloads, may enable Hyper-Threading on a per machine basis. The setting is located at chrome://flags#scheduler-configuration. The ‘performance’ setting chooses the configuration that enables Hyper-Threading. The ‘conservative’ setting chooses the configuration that disables Hyper-Threading,” the company explained.
The ZombieLoad, RIDL and Fallout attack methods work against both PCs and cloud environments. An attacker can leverage these techniques to get applications, the operating system, virtual machines and trusted execution environments to leak information, including passwords, website content, disk encryption keys and browser history.
In the case of Chrome OS, impacted devices include several Chromebook, Chromebox and Chromebase devices made by AOpen, ASI, ASUS, Acer, Bobicus, CTL, Dell, Edxis, Google, HP, LG, Lenovo, Samsung, Toshiba and others.