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Category:   Application (Generic)  >   Red Hat Enterprise Virtualization Vendors:   Red Hat
(Red Hat Issues Fix for Red Hat Enterprise Virtualization) Intel/AMD/ARM CPU Cache Race Conditions Let Local Users Read Arbitrary Register and Memory Contents
SecurityTracker Alert ID:  1040955
SecurityTracker URL:
CVE Reference:   CVE-2018-3639   (Links to External Site)
Date:  May 22 2018
Impact:   Disclosure of system information
Fix Available:  Yes  Vendor Confirmed:  Yes  

Description:   Two vulnerabilities were reported in Intel, AMD, and ARM CPUs. A local user can obtain potentially sensitive information from system memory. Red Hat Enterprise Virtualization is affected.

A local user can exploit race conditions in CPU cache processing to obtain potentially sensitive information on the target system. This can be exploited to read arbitrary system register and memory contents on the target system.

A local user can conduct a side-channel attack to exploit a flaw in the speculative loading of system registers to read privileged system registers [CVE-2018-3640].

The CVE-2018-3640 vulnerability is referred to as "Spectre variant 3A".

A local user can conduct a side-channel attack to exploit a flaw in the speculative execution of Load and Store instructions to read privileged memory [CVE-2018-3639].

The CVE-2018-3639 vulnerability is referred to as "Spectre variant 4".

The original advisory is available at:

Zdenek Sojka, Rudolf Marek, and Alex Zuepke from SYSGO AG, Jann Horn (Google Project Zero), and Ken Johnson (Microsoft Security Response Center) reported these vulnerabilities.

Impact:   A local user can view system register or memory contents on the target CPU device.
Solution:   Red Hat has issued a fix for CVE-2018-3639 for Red Hat Enterprise Virtualization.

The Red Hat advisory is available at:

Vendor URL: (Links to External Site)
Cause:   Access control error, State error
Underlying OS:  Linux (Red Hat Enterprise)
Underlying OS Comments:  7

Message History:   This archive entry is a follow-up to the message listed below.
May 22 2018 Intel/AMD/ARM CPU Cache Race Conditions Let Local Users Read Arbitrary Register and Memory Contents

 Source Message Contents

Subject:  [RHSA-2018:1655-01] Important: qemu-kvm-rhev security update

Hash: SHA256

                   Red Hat Security Advisory

Synopsis:          Important: qemu-kvm-rhev security update
Advisory ID:       RHSA-2018:1655-01
Product:           Red Hat Virtualization
Advisory URL:
Issue date:        2018-05-21
CVE Names:         CVE-2018-3639 

1. Summary:

An update for qemu-kvm-rhev is now available for Red Hat Virtualization 4
for Red Hat Enterprise Linux 7.

Red Hat Product Security has rated this update as having a security impact
of Important. A Common Vulnerability Scoring System (CVSS) base score,
which gives a detailed severity rating, is available for each vulnerability
from the CVE link(s) in the References section.

2. Relevant releases/architectures:

Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts - ppc64le, x86_64

3. Description:

KVM (Kernel-based Virtual Machine) is a full virtualization solution for
Linux on a variety of architectures. The qemu-kvm-rhev packages provide the
user-space component for running virtual machines that use KVM in
environments managed by Red Hat products.

Security Fix(es):

* An industry-wide issue was found in the way many modern microprocessor
designs have implemented speculative execution of Load & Store instructions
(a commonly used performance optimization). It relies on the presence of a
precisely-defined instruction sequence in the privileged code as well as
the fact that memory read from address to which a recent memory write has
occurred may see an older value and subsequently cause an update into the
microprocessor's data cache even for speculatively executed instructions
that never actually commit (retire). As a result, an unprivileged attacker
could use this flaw to read privileged memory by conducting targeted cache
side-channel attacks. (CVE-2018-3639)

Note: This is the qemu-kvm-rhev side of the CVE-2018-3639 mitigation.

Red Hat would like to thank Ken Johnson (Microsoft Security Response
Center) and Jann Horn (Google Project Zero) for reporting this issue.

4. Solution:

For details on how to apply this update, which includes the changes
described in this advisory, refer to:

After installing this update, shut down all running virtual machines. Once
all virtual machines have shut down, start them again for this update to
take effect.

5. Bugs fixed (

1566890 - CVE-2018-3639 hw: cpu: speculative store bypass

6. Package List:

Red Hat Virtualization 4 Management Agent for RHEL 7 Hosts:




These packages are GPG signed by Red Hat for security.  Our key and
details on how to verify the signature are available from

7. References:

8. Contact:

The Red Hat security contact is <>. More contact
details at

Copyright 2018 Red Hat, Inc.
Version: GnuPG v1


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