New ZombieLoad v2 Attack Affects Intel’s Latest Cascade Lake CPUs

This time a new variant (v2) of the data-leaking side-channel
vulnerability also affects the most recent Intel CPUs, including
the latest Cascade Lake, which are otherwise resistant against
attacks like Meltdown^[1], Foreshadow^[2]
and other MDS variants (RIDL and Fallout).

Initially discovered in May this year, ZombieLoad is
one of the three novel types of microarchitectural data sampling
(MDS) speculative execution vulnerabilities that affect Intel
processor generations released from 2011 onwards.
^[3]

The first variant of ZombieLoad is a Meltdown-type attack that
targets the fill-buffer logic allowing attackers to steal sensitive
data not only from other applications and the operating system but
also from virtual machines running in the cloud with common
hardware.

ZombieLoad v2 Affects Latest Intel CPUs

Now, the same group of researchers has disclosed details of a
second variant of the vulnerability, dubbed ZombieLoad v2^[4]
and tracked as CVE-2019-11135, that resides in Intel’s
Transactional Synchronization Extensions (TSX).

Intel TSX provides transactional memory support in hardware,
aiming to improve the performance of the CPU by speeding up the
execution of multi-threaded software and aborting a transaction
when a conflict memory access was found.

ZombieLoad v2 affects desktops, laptops, and cloud computers
running Intel CPUs that support TSX, including Core, Xeon
processors, and Cascade Lake, Intel’s line of high-end CPUs that
was introduced in April 2019.

However, Intel’s Whiskey Lake, Coffee Lake-R, and Cascade
Lake-SP lines of processors are not vulnerable as they do not
support TSX.

Microcode Patches Available for ZombieLoad v2

Researchers warned Intel about ZombieLoad Variant 2 on April 23,
the same time they discovered and reported the other MDS flaws that
the chipmaker patched a month later in May.

Intel asked the researchers not to disclose the details of
Variant 2 until now when the chipmaker came up with security
patches^[5] with a microcode update
that addresses this vulnerability.

The company has also provided MDS
mitigations^[6] for operating system
developers, virtual machine manager (VMM) developers, software
developers using Intel SGX, and system administrators.

For more details on the new ZombieLoad variant, you can head on
to the original research paper published by researchers in May,
which has now been updated to add information on the second variant
as well.

Meanwhile, Red Hat has also released a
script using which users can detect if their Intel-powered
system is also vulnerable to this flaw.
^[7]