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Security Advisory

USN-4385-2: Intel Microcode regression

USN-4385-2: Intel Microcode regression




Canonical Ubuntu

Versions Affected

  • Canonical Ubuntu 14.04
  • Canonical Ubuntu 16.04


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)

CVEs contained in this USN include: CVE-2020-0543, CVE-2020-0548, CVE-2020-0549.

Affected Cloud Foundry Products and Versions

Severity is medium unless otherwise noted.

  • Xenial Stemcells
    • 170.x versions prior to 170.221
    • 250.x versions prior to 250.200
    • 315.x versions prior to 315.185
    • 456.x versions prior to 456.114
    • 621.x versions prior to 621.76
    • All other stemcells not listed.


Users of affected products are strongly encouraged to follow the mitigations below. The Cloud Foundry project recommends upgrading the following releases:

  • Xenial Stemcells
    • Upgrade 170.x versions to 170.221 or greater
    • Upgrade 250.x versions to 250.200 or greater
    • Upgrade 315.x versions to 315.185 or greater
    • Upgrade 456.x versions to 456.114 or greater
    • Upgrade 621.x versions to 621.76 or greater
    • All other stemcells should be upgraded to the latest version available on


2020-06-10: Initial vulnerability report published.

Cloud Foundry Foundation Security Team Profile Image

Cloud Foundry Foundation Security Team, AUTHOR