CVE-2018-20784: Medium severity Linux Linux kernel vulnerability

Published Dec 28, 2018
·
Updated

In the Linux kernel before 4.20.2, kernel/sched/fair.c mishandles leaf cfsrq's, which allows attackers to cause a denial of service (infinite loop in updateblockedaverages) or possibly have unspecified other impact by inducing a high load.

Other sources

The CFS Linux kernel scheduler mishandles handling of leaf cfsrq's in the kernel/sched/fair.c code, which allows a local unprivileged attacker to cause a denial of service (DoS) by entering an infinite loop in updateblockedaverages() function by inducing a high load on a system. Due to the nature of the flaw, a remote network attack (by initiating a magnitude of remote requests) cannot be fully ruled out.

The CFS Linux kernel scheduler mishandles handling of leaf cfsrq's in the kernel/sched/fair.c code, which allows a local unprivileged attacker to cause a denial of service (DoS) by entiring the infinite loop in updateblockedaverages() function by inducing a high load on a system. Due to the nature of the flaw, a remote network attack (by initiating a magnitude of remote requests) cannot be fully ruled out, although we believe it is unlikely.

References:

https://lore.kernel.org/lkml/1545879866-27809-1-git-send-email-xiexiuqi@huawei.com/T/#u

An upstream patch:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c40f7d74c741a907cfaeb73a7697081881c497d0

— Red Hat

Affected Software

51 affected componentsFixes available
redhat/kernel-rt<0:4.18.0-80.7.1.rt9.153.el8_0
0:4.18.0-80.7.1.rt9.153.el8_0
redhat/kernel<0:4.18.0-80.7.1.el8_0
0:4.18.0-80.7.1.el8_0
Linux Linux kernel>=4.13<4.14.93
Linux Linux kernel>=4.19<4.19.15
Linux Linux kernel>=4.20<4.20.2
Linux Linux kernel=5.0-rc1
Canonical Ubuntu Linux=14.04
Canonical Ubuntu Linux=16.04
Canonical Ubuntu Linux=18.04
redhat Enterprise Linux=8.0
redhat Enterprise Linux For Real Time=8
debian/linux
6.1.176-16.1.190-16.12.107-16.12.113-17.2.12-1
ubuntu/linux-aws<4.4.0-1059.63
4.4.0-1059.63
ubuntu/linux-azure<4.15.0-1059.64~14.04.1
4.15.0-1059.64~14.04.1
ubuntu/linux-lts-xenial<4.4.0-170.199~14.04.1
4.4.0-170.199~14.04.1
ubuntu/linux<4.4.0-170.199
4.4.0-170.199
ubuntu/linux-aws<4.4.0-1099.110
4.4.0-1099.110
ubuntu/linux-aws-hwe<4.15.0-1047.49~16.04.1
4.15.0-1047.49~16.04.1
ubuntu/linux-azure<4.15.0-1056.61
4.15.0-1056.61
ubuntu/linux-gcp<4.15.0-1041.43
4.15.0-1041.43
ubuntu/linux-hwe<4.15.0-60.67~16.04.1
4.15.0-60.67~16.04.1
ubuntu/linux-kvm<4.4.0-1063.70
4.4.0-1063.70
ubuntu/linux-oracle<4.15.0-1022.25~16.04.1
4.15.0-1022.25~16.04.1
ubuntu/linux-raspi2<4.4.0-1126.135
4.4.0-1126.135
ubuntu/linux-snapdragon<4.4.0-1130.138
4.4.0-1130.138
ubuntu/linux-fips<4.4.0-1026.31
4.4.0-1026.31
ubuntu/linux-fips*
ubuntu/linux<4.15.0-60.67
4.15.0-60.67
ubuntu/linux-aws<4.15.0-1047.49
4.15.0-1047.49
ubuntu/linux-azure<5.0.0-1014.14~18.04.1
5.0.0-1014.14~18.04.1
ubuntu/linux-gcp<4.15.0-1042.45
4.15.0-1042.45
ubuntu/linux-gke-4.15<4.15.0-1041.43
4.15.0-1041.43
ubuntu/linux-hwe<5.0.0-23.24~18.04.1
5.0.0-23.24~18.04.1
ubuntu/linux-kvm<4.15.0-1043.43
4.15.0-1043.43
ubuntu/linux-oem<4.15.0-1056.65
4.15.0-1056.65
ubuntu/linux-oracle<4.15.0-1022.25
4.15.0-1022.25
ubuntu/linux-raspi2<4.15.0-1044.47
4.15.0-1044.47
ubuntu/linux-snapdragon<4.15.0-1062.69
4.15.0-1062.69
ubuntu/linux-aws-fips<4.15.0-2018.18
4.15.0-2018.18
ubuntu/linux-azure-fips<4.15.0-2006.7
4.15.0-2006.7
ubuntu/linux-aws-fips*
ubuntu/linux-azure-fips*
ubuntu/linux-gcp-fips*
ubuntu/linux-azure-fde*
ubuntu/linux-gke*
ubuntu/linux-riscv*
ubuntu/linux-intel-iot-realtime*
ubuntu/linux-realtime*
ubuntu/linux-riscv*
ubuntu/linux-raspi-realtime*
ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade redhat/kernel-rt to a version that resolves this vulnerability.

    Fixed in 0:4.18.0-80.7.1.rt9.153.el8_0
  2. Upgrade

    Upgrade redhat/kernel to a version that resolves this vulnerability.

    Fixed in 0:4.18.0-80.7.1.el8_0
  3. Upgrade

    Upgrade debian/linux to a version that resolves this vulnerability.

    Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.113-1Fixed in 7.2.12-1
  4. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 4.4.0-1059.63
  5. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 4.15.0-1059.64~14.04.1
  6. Upgrade

    Upgrade ubuntu/linux-lts-xenial to a version that resolves this vulnerability.

    Fixed in 4.4.0-170.199~14.04.1
  7. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 4.4.0-170.199
  8. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 4.4.0-1099.110
  9. Upgrade

    Upgrade ubuntu/linux-aws-hwe to a version that resolves this vulnerability.

    Fixed in 4.15.0-1047.49~16.04.1
  10. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 4.15.0-1056.61
  11. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 4.15.0-1041.43
  12. Upgrade

    Upgrade ubuntu/linux-hwe to a version that resolves this vulnerability.

    Fixed in 4.15.0-60.67~16.04.1
  13. Upgrade

    Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.

    Fixed in 4.4.0-1063.70
  14. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 4.15.0-1022.25~16.04.1
  15. Upgrade

    Upgrade ubuntu/linux-raspi2 to a version that resolves this vulnerability.

    Fixed in 4.4.0-1126.135
  16. Upgrade

    Upgrade ubuntu/linux-snapdragon to a version that resolves this vulnerability.

    Fixed in 4.4.0-1130.138
  17. Upgrade

    Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.

    Fixed in 4.4.0-1026.31
  18. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 4.15.0-60.67
  19. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 4.15.0-1047.49
  20. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 5.0.0-1014.14~18.04.1
  21. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 4.15.0-1042.45
  22. Upgrade

    Upgrade ubuntu/linux-gke-4.15 to a version that resolves this vulnerability.

    Fixed in 4.15.0-1041.43
  23. Upgrade

    Upgrade ubuntu/linux-hwe to a version that resolves this vulnerability.

    Fixed in 5.0.0-23.24~18.04.1
  24. Upgrade

    Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.

    Fixed in 4.15.0-1043.43
  25. Upgrade

    Upgrade ubuntu/linux-oem to a version that resolves this vulnerability.

    Fixed in 4.15.0-1056.65
  26. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 4.15.0-1022.25
  27. Upgrade

    Upgrade ubuntu/linux-raspi2 to a version that resolves this vulnerability.

    Fixed in 4.15.0-1044.47
  28. Upgrade

    Upgrade ubuntu/linux-snapdragon to a version that resolves this vulnerability.

    Fixed in 4.15.0-1062.69
  29. Upgrade

    Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.

    Fixed in 4.15.0-2018.18
  30. Upgrade

    Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.

    Fixed in 4.15.0-2006.7
  31. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 4.20.2

Event History

Dec 28, 2018
CVE Published
12:00 AM
Feb 22, 2019
Data Sourced
via Ubuntu·12:00 AM
RemedyDescriptionSeverityAffected Software
Data Sourced
via OSV·12:00 AM
DescriptionSeverityAffected Software
CVE Published
via MITRE·03:00 PM
Data Sourced
via MITRE·03:00 PM
Description
Data Sourced
via NVD·03:29 PM
RemedyDescriptionSeverityWeaknessAffected Software
Feb 25, 2019
Data Sourced
via Red Hat·10:01 AM
DescriptionSeverityAffected Software

Parent advisories

This vulnerability appears in the following advisories.

Frequently Asked Questions

1

What is the severity of CVE-2018-20784?

CVE-2018-20784 has a severity rating that can lead to denial of service due to infinite loops in certain Linux kernel scheduling mechanisms.

2

How do I fix CVE-2018-20784?

To fix CVE-2018-20784, update your Linux kernel to versions 4.20.2 or newer, or apply the appropriate patches as specified by your distribution.

3

Which Linux distributions are affected by CVE-2018-20784?

CVE-2018-20784 affects multiple Linux distributions including Red Hat Enterprise Linux, Ubuntu, and various versions of the Linux kernel.

4

Can CVE-2018-20784 be exploited remotely?

CVE-2018-20784 is exploitable locally, allowing attackers to induce high loads leading to a denial of service on the affected systems.

5

What versions of the Linux kernel are vulnerable to CVE-2018-20784?

Linux kernel versions prior to 4.20.2, specifically those between 4.13 and 4.19, as well as certain earlier kernel versions, are vulnerable to CVE-2018-20784.

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