Release date: 2019-11-12


Details and mitigation information about a sub-class of speculative execution side-channel vulnerabilities called TSX Asynchronous Abort (TAA).

Please refer to the Intel Security Advisory 00270 located at: Intel website.

The TAA vulnerability is a sub-set of the MDS vulnerability, already mitigated in NetBSD.

Status of the Fix

NetBSD-8 and above have received a fix. NetBSD-7, and all the anterior releases, have no planned fixes.


The mitigation for TAA depends on the Intel CPU model and available microcode or motherboard BIOS revision.

You may also want to disable SMT/HyperThreading to address certain aspects of the vulnerabilities. Should you not be able to disable SMT/HT in your BIOS, you can put smtoff=YES in your /etc/rc.conf file.

Enabling the mitigation

The two following sysctls are now available:

machdep.taa.mitigated = {0/1} user-settable
machdep.taa.method = {string} constructed by the kernel

The TAA mitigation may be provided by the already-existing MDS mitigation. Before enabling the TAA mitigation, you should first enable the MDS mitigation if not already enabled. This may imply loading an updated microcode, if not already provided by the BIOS.

Two cases must then be considered, depending the content of machdep.taa.method: