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Microarchitectural Data Sampling

Microarchitectural Data Sampling

(CVE-2018-12126, CVE-2018-12127, CVE-2018-12130, and CVE-2019-11091)


Microarchitectural Data Sampling (MDS) refers to a set of speculative execution side-channel vulnerabilities which potentially allow results from previous execution on a core to be observed across security boundaries via microarchitectural state, on certain Intel CPUs. They are described in Intel's announcement, and referred to as MSBDS/CVE-2018-12126, MLPDS/CVE-2018-12127, MFBDS/CVE-2018-12130, and MDSUM/CVE-2019-11091.

An attacker successfully exploiting these vulnerabilities could read sensitive data from other processes running on the system, breaking the isolation between processes provided by modern operating systems. If Chrome processes are attacked, these sensitive data could include website contents as well as passwords, credit card numbers, or cookies.

Chrome, like all programs, relies on the operating system to provide isolation between processes. Operating system vendors may release updates to improve isolation, so users should ensure they install any updates and follow any additional guidance from their operating system vendor in relation to MDS mitigation.

Some operating system mitigations will also require changes in Chrome which we shall include in subsequent Chrome releases. Users should ensure their version of Chrome is always up to date.


The Chrome team investigated various mitigation options Chrome could take independently of the OS, but none were sufficiently complete or performant. Users should rely on operating system level mitigations.


On the Android platform, the vast majority of devices are not affected, as these issues only apply to some Intel-based systems.

As always, Android users should apply updates for their devices as soon as they are available from their OEM.

Chrome OS

Chrome OS has disabled Hyper-Threading on Chrome OS 74 and subsequent versions. This provides protection against attacks using MDS. More details on Chrome OS's response.


macOS Mojave 10.14.5 includes MDS mitigations. These have been adopted by Chrome and will be included in Chrome 75 which will be released to the Stable channel on or around the 4th of June.


Windows users should apply updates with MDS mitigations as soon as they are available, and follow any guidance to adjust system settings if appropriate.


Apple iOS devices use CPUs not known to be vulnerable to MDS.


Linux users should apply kernel and CPU microcode updates as soon as they are available from their distribution vendor, and follow any guidance to adjust system settings.