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CVE-2019-3887

Publication date 9 April 2019

Last updated 24 July 2024

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

5.6 · Medium

Score breakdown

A flaw was found in the way KVM hypervisor handled x2APIC Machine Specific Rregister (MSR) access with nested(=1) virtualization enabled. In that, L1 guest could access L0's APIC register values via L2 guest, when 'virtualize x2APIC mode' is enabled. A guest could use this flaw to potentially crash the host kernel resulting in DoS issue. Kernel versions from 4.16 and newer are vulnerable to this issue.

From the Ubuntu Security Team

Marc Orr discovered that the KVM hypervisor implementation in the Linux kernel did not properly restrict APIC MSR register values when nested virtualization is used. An attacker in a guest vm could use this to cause a denial of service (host OS crash).

Read the notes from the security team

Mitigation

If qemu is installed, to prevent nested virtualization from being enabled, set "options kvm_intel nested=0" in /etc/modprobe.d/qemu-system-x86.conf

Status

Package Ubuntu Release Status
linux 19.04 disco
Fixed 5.0.0-15.16
18.10 cosmic
Fixed 4.18.0-20.21
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty
Not affected
linux-aws 19.04 disco
Fixed 5.0.0-1006.6
18.10 cosmic
Fixed 4.18.0-1016.18
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty
Not affected
linux-aws-hwe 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-azure 19.04 disco
Fixed 5.0.0-1006.6
18.10 cosmic
Fixed 4.18.0-1018.18
18.04 LTS bionic
Fixed 4.18.0-1018.18~18.04.1
16.04 LTS xenial
Not affected
14.04 LTS trusty
Not affected
linux-azure-edge 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic
Fixed 4.18.0-1018.18~18.04.1
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-euclid 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-flo 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Ignored
14.04 LTS trusty Not in release
linux-gcp 19.04 disco
Fixed 5.0.0-1006.6
18.10 cosmic
Fixed 4.18.0-1011.12
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-gcp-edge 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic
Fixed 4.18.0-1011.12~18.04.1
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gke 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Ignored
14.04 LTS trusty Not in release
linux-goldfish 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Ignored
14.04 LTS trusty Not in release
linux-grouper 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-hwe 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic
Fixed 4.18.0-20.21~18.04.1
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-hwe-edge 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-kvm 19.04 disco
Fixed 5.0.0-1006.6
18.10 cosmic
Fixed 4.18.0-1012.12
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-lts-trusty 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-lts-utopic 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Ignored
linux-lts-vivid 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Ignored
linux-lts-wily 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Ignored
linux-lts-xenial 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty
Not affected
linux-maguro 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-mako 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Ignored
14.04 LTS trusty Not in release
linux-manta 19.04 disco Not in release
18.10 cosmic Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-oem 19.04 disco
Not affected
18.10 cosmic
Not affected
18.04 LTS bionic
Not affected
16.04 LTS xenial Ignored
14.04 LTS trusty Not in release
linux-oracle 19.04 disco
Not affected
18.10 cosmic
Not affected
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-raspi2 19.04 disco
Fixed 5.0.0-1008.8
18.10 cosmic
Fixed 4.18.0-1014.16
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-snapdragon 19.04 disco
Fixed 5.0.0-1012.12
18.10 cosmic Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release

Notes

tyhicks

Ubuntu kernels do not enable nested KVM virtualization by default and are unaffected by this flaw in the default configuration. However, installing QEMU results in nested KVM support to be enabled via the /etc/modprobe.d/qemu-system-x86.conf file. To ensure that nested virtualization is not enabled, verify that the /sys/module/kvm_intel/parameters/nested file contains "N".

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
linux

Severity score breakdown

Parameter Value
Base score 5.6 · Medium
Attack vector Local
Attack complexity High
Privileges required Low
User interaction None
Scope Changed
Confidentiality None
Integrity impact None
Availability impact High
Vector CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H

References

Related Ubuntu Security Notices (USN)

    • USN-3980-1
    • Linux kernel vulnerabilities
    • 14 May 2019
    • USN-3980-2
    • Linux kernel (HWE) vulnerabilities
    • 14 May 2019
    • USN-3979-1
    • Linux kernel vulnerabilities
    • 14 May 2019

Other references