What’s Vulnerable › Vulnerabilities

CVE-2018-20784

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 4.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-02-22 · updated 2026-06-17
• Weakness: CWE-835

Description

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

Affected products

• Canonical Ubuntu Linux: 14.04, 16.04, 18.04
• Linux kernel: from 4.13 before 4.14.93; from 4.19 before 4.19.15; from 4.20 before 4.20.2; 5.0-rc1 — fixed in 4.14.93, 4.19.15, 4.20.2
• Red Hat Enterprise Linux: 8.0
• RedHat Enterprise Linux For Real Time: 8

How to fix

Upgrade to a fixed version: Linux kernel 4.14.93, 4.19.15, 4.20.2. Check the vendor advisory for mitigations.

References

• http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c40f7d74c741a907cfaeb73a7697081881c497d0
• https://access.redhat.com/errata/RHSA-2019:1959
• https://access.redhat.com/errata/RHSA-2019:1971
• https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.20.2
• https://github.com/torvalds/linux/commit/c40f7d74c741a907cfaeb73a7697081881c497d0
• https://usn.ubuntu.com/4115-1/
• https://usn.ubuntu.com/4118-1/
• https://usn.ubuntu.com/4211-1/
• https://usn.ubuntu.com/4211-2/
• http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c40f7d74c741a907cfaeb73a7697081881c497d0
• https://access.redhat.com/errata/RHSA-2019:1959
• https://access.redhat.com/errata/RHSA-2019:1971

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