A Intel Microcode regression update has been released for Ubuntu Linux 20.04 LTS, 19.10, 18.04 LTS, 16.04 LTS, and 14.04 ESM.

USN-4385-2: Intel Microcode regression

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Ubuntu Security Notice USN-4385-2
June 10, 2020

intel-microcode regression
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS
- Ubuntu 19.10
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
- Ubuntu 14.04 ESM

Summary:

USN-4385-1 introduced a regression in the Intel Microcode for some processors.

Software Description:
- intel-microcode: Processor microcode for Intel CPUs

Details:

USN-4385-1 provided updated Intel Processor Microcode. Unfortunately,
that update prevented certain processors in the Intel Skylake family
(06_4EH) from booting successfully. Additonally, on Ubuntu 20.04
LTS, late loading of microcode was enabled, which could lead to
system instability. This update reverts the microcode update for
the Skylake processor family and disables the late loading option on
Ubuntu 20.04 LTS.

Please note that the 'dis_ucode_ldr' kernel command line option can be
added in the boot menu to disable microcode loading for system recovery.

We apologize for the inconvenience.

Original advisory details:

It was discovered that memory contents previously stored in
microarchitectural special registers after RDRAND, RDSEED, and SGX EGETKEY
read operations on Intel client and Xeon E3 processors may be briefly
exposed to processes on the same or different processor cores. A local
attacker could use this to expose sensitive information. (CVE-2020-0543)

It was discovered that on some Intel processors, partial data values
previously read from a vector register on a physical core may be propagated
into unused portions of the store buffer. A local attacker could possible
use this to expose sensitive information. (CVE-2020-0548)

It was discovered that on some Intel processors, data from the most
recently evicted modified L1 data cache (L1D) line may be propagated into
an unused (invalid) L1D fill buffer. A local attacker could possibly use
this to expose sensitive information. (CVE-2020-0549)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 20.04 LTS:
intel-microcode 3.20200609.0ubuntu0.20.04.2

Ubuntu 19.10:
intel-microcode 3.20200609.0ubuntu0.19.10.2

Ubuntu 18.04 LTS:
intel-microcode 3.20200609.0ubuntu0.18.04.1

Ubuntu 16.04 LTS:
intel-microcode 3.20200609.0ubuntu0.16.04.1

Ubuntu 14.04 ESM:
intel-microcode 3.20200609.0ubuntu0.14.04.1

After a standard system update you need to reboot your computer to
make all the necessary changes.

References:
  https://usn.ubuntu.com/4385-2
  https://usn.ubuntu.com/4385-1
  https://launchpad.net/bugs/1882890,   https://launchpad.net/bugs/1883002

Package Information:
  https://launchpad.net/ubuntu/+source/intel-microcode/3.20200609.0ubuntu0.20.04.2
  https://launchpad.net/ubuntu/+source/intel-microcode/3.20200609.0ubuntu0.19.10.2
  https://launchpad.net/ubuntu/+source/intel-microcode/3.20200609.0ubuntu0.18.04.1
  https://launchpad.net/ubuntu/+source/intel-microcode/3.20200609.0ubuntu0.16.04.1