New ZombieLoad Side-Channel Attack Variant: TSX Asynchronous Abort

In addition to the JCC erratum being made public today and that performance-shifting Intel microcode update affecting Skylake through Cascade Lake, researchers also announced a new ZombieLoad side-channel attack variant dubbed "TSX Asynchronous Abort" or TAA for short.

ZombieLoad / MDS (Microarchitectural Data Sampling) was announced back in May by researchers while today Cyberus Technology has announced a new variant focused on Intel processors with TSX (Transactional Synchronization Extensions). TSX Asynchronous Abort is a new ZombieLoad variant that was actually discovered back as part of Cyberus' originally discoveries but faced an extended embargo.

Current Intel hardware mitigations do not cover TAA and current Cascade Lake CPUs remain vulnerable. TAA can allow leaking of data across processes, privilege boundaries and Hyper Threading. With Hyper Threading disabled, TAA can still leak data from protected domains.

For mitigating TAA Asynchronous Abort there is no new software workaround out today short of disabling Intel TSX. It is recommended to disable Hyper Threading while Cyberus ultimately recommends running trusted/untrusted applications on separate physical systems.

More details on TAA via Cyberus' disclosure and the CVE-2019-11135 notice.