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CVE-2019-14821

Publication date 1 October 2019

Last updated 24 July 2024


Ubuntu priority

Cvss 3 Severity Score

8.8 · High

Score breakdown

An out-of-bounds access issue was found in the Linux kernel, all versions through 5.3, in the way Linux kernel's KVM hypervisor implements the Coalesced MMIO write operation. It operates on an MMIO ring buffer 'struct kvm_coalesced_mmio' object, wherein write indices 'ring->first' and 'ring->last' value could be supplied by a host user-space process. An unprivileged host user or process with access to '/dev/kvm' device could use this flaw to crash the host kernel, resulting in a denial of service or potentially escalating privileges on the system.

From the Ubuntu Security Team

Matt Delco discovered that the KVM hypervisor implementation in the Linux kernel did not properly perform bounds checking when handling coalesced MMIO write operations. A local attacker with write access to /dev/kvm could use this to cause a denial of service (system crash).

Read the notes from the security team

Mitigation

Ensure that untrusted users cannot write to the /dev/kvm device

Status

Package Ubuntu Release Status
linux 20.04 LTS focal
Not affected
19.10 eoan
Not affected
19.04 disco
Fixed 5.0.0-32.34
18.04 LTS bionic
Fixed 4.15.0-66.75
16.04 LTS xenial
Fixed 4.4.0-166.195
14.04 LTS trusty Ignored
linux-aws 20.04 LTS focal
Not affected
19.10 eoan
Not affected
19.04 disco
Fixed 5.0.0-1019.21
18.04 LTS bionic
Fixed 4.15.0-1052.54
16.04 LTS xenial
Fixed 4.4.0-1096.107
14.04 LTS trusty
linux-aws-5.0 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-aws-hwe 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial
Fixed 4.15.0-1052.54~16.04.1
14.04 LTS trusty Not in release
linux-azure 20.04 LTS focal
Not affected
19.10 eoan
Not affected
19.04 disco
Fixed 5.0.0-1023.24
18.04 LTS bionic
Fixed 5.0.0-1023.24~18.04.1
16.04 LTS xenial
Fixed 4.15.0-1061.66
14.04 LTS trusty
linux-azure-5.3 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-azure-edge 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco Not in release
18.04 LTS bionic
Fixed 5.0.0-1023.24~18.04.1
16.04 LTS xenial
Fixed 4.15.0-1061.66
14.04 LTS trusty Not in release
linux-gcp 20.04 LTS focal
Not affected
19.10 eoan
Not affected
19.04 disco
Fixed 5.0.0-1021.21
18.04 LTS bionic
Fixed 5.0.0-1021.21~18.04.1
16.04 LTS xenial
Fixed 4.15.0-1047.50
14.04 LTS trusty Not in release
linux-gcp-5.3 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gcp-edge 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco Not in release
18.04 LTS bionic
Fixed 5.0.0-1021.21~18.04.1
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gke-4.15 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco Not in release
18.04 LTS bionic
Fixed 4.15.0-1046.49
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gke-5.0 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco Not in release
18.04 LTS bionic
Fixed 5.0.0-1023.23~18.04.2
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gke-5.3 20.04 LTS focal Not in release
19.10 eoan Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-hwe 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco Not in release
18.04 LTS bionic
Fixed 5.0.0-32.34~18.04.2
16.04 LTS xenial
Fixed 4.15.0-66.75~16.04.1
14.04 LTS trusty Not in release
linux-hwe-edge 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco Not in release
18.04 LTS bionic Ignored
16.04 LTS xenial
Fixed 4.15.0-66.75~16.04.1
14.04 LTS trusty Not in release
linux-kvm 20.04 LTS focal
Not affected
19.10 eoan
Not affected
19.04 disco
Fixed 5.0.0-1020.21
18.04 LTS bionic
Fixed 4.15.0-1048.48
16.04 LTS xenial
Fixed 4.4.0-1060.67
14.04 LTS trusty Not in release
linux-lts-trusty 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco 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-xenial 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty
linux-oem 20.04 LTS focal Not in release
19.10 eoan
Fixed 4.15.0-1059.68
19.04 disco Ignored
18.04 LTS bionic
Fixed 4.15.0-1059.68
16.04 LTS xenial Ignored
14.04 LTS trusty Not in release
linux-oem-5.6 20.04 LTS focal
Not affected
19.10 eoan 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-osp1 20.04 LTS focal Not in release
19.10 eoan
Fixed 5.0.0-1025.28
19.04 disco Ignored
18.04 LTS bionic
Fixed 5.0.0-1025.28
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-oracle 20.04 LTS focal
Not affected
19.10 eoan
Not affected
19.04 disco Ignored
18.04 LTS bionic
Fixed 4.15.0-1027.30
16.04 LTS xenial
Fixed 4.15.0-1027.30~16.04.1
14.04 LTS trusty Not in release
linux-oracle-5.0 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-oracle-5.3 20.04 LTS focal Not in release
19.10 eoan Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-raspi2 20.04 LTS focal
Not affected
19.10 eoan
Not affected
19.04 disco
Fixed 5.0.0-1020.20
18.04 LTS bionic
Fixed 4.15.0-1049.53
16.04 LTS xenial
Fixed 4.4.0-1124.133
14.04 LTS trusty Not in release
linux-raspi2-5.3 20.04 LTS focal Not in release
19.10 eoan Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-snapdragon 20.04 LTS focal Not in release
19.10 eoan Not in release
19.04 disco
Fixed 5.0.0-1024.25
18.04 LTS bionic
Fixed 4.15.0-1066.73
16.04 LTS xenial
Fixed 4.4.0-1128.136
14.04 LTS trusty Not in release

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Notes


tyhicks

An attacker needs write access to the /dev/kvm device file to exploit this flaw. By default, Ubuntu users don't have privileges to write to /dev/kvm. This is true even when libvirt is installed and in use.

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

References

Related Ubuntu Security Notices (USN)

    • USN-4157-2
    • Linux kernel (HWE) vulnerabilities
    • 22 October 2019
    • USN-4162-1
    • Linux kernel vulnerabilities
    • 22 October 2019
    • USN-4162-2
    • Linux kernel (Azure) vulnerabilities
    • 23 October 2019
    • USN-4163-2
    • Linux kernel (Xenial HWE) vulnerabilities
    • 23 October 2019
    • USN-4163-1
    • Linux kernel vulnerabilities
    • 22 October 2019
    • USN-4157-1
    • Linux kernel vulnerabilities
    • 17 October 2019

Other references