Covert Timing Channel Affecting kernel-rt-debug-kvm package, versions <0:4.18.0-147.5.1.rt24.98.el8_1


Severity

Recommended
high

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.05% (20th percentile)

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  • Snyk IDSNYK-RHEL8-KERNELRTDEBUGKVM-3640334
  • published26 Jul 2021
  • disclosed18 Nov 2019

Introduced: 18 Nov 2019

CVE-2019-19338  (opens in a new tab)
CWE-385  (opens in a new tab)
CWE-203  (opens in a new tab)

How to fix?

Upgrade RHEL:8 kernel-rt-debug-kvm to version 0:4.18.0-147.5.1.rt24.98.el8_1 or higher.
This issue was patched in RHSA-2020:0328.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-debug-kvm package and not the kernel-rt-debug-kvm package as distributed by RHEL. See How to fix? for RHEL:8 relevant fixed versions and status.

A flaw was found in the fix for CVE-2019-11135, in the Linux upstream kernel versions before 5.5 where, the way Intel CPUs handle speculative execution of instructions when a TSX Asynchronous Abort (TAA) error occurs. When a guest is running on a host CPU affected by the TAA flaw (TAA_NO=0), but is not affected by the MDS issue (MDS_NO=1), the guest was to clear the affected buffers by using a VERW instruction mechanism. But when the MDS_NO=1 bit was exported to the guests, the guests did not use the VERW mechanism to clear the affected buffers. This issue affects guests running on Cascade Lake CPUs and requires that host has 'TSX' enabled. Confidentiality of data is the highest threat associated with this vulnerability.

CVSS Scores

version 3.1