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.
https://github.com/torvalds/linux/commit/c40f7d74c741a907cfaeb73a7697081881c497d0
https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.20.2
https://access.redhat.com/errata/RHSA-2019:1959
https://access.redhat.com/errata/RHSA-2019:1971
https://usn.ubuntu.com/4115-1/
https://usn.ubuntu.com/4118-1/
Source: MITRE
Published: 2019-02-22
Updated: 2021-06-02
Type: CWE-835
Base Score: 7.5
Vector: AV:N/AC:L/Au:N/C:P/I:P/A:P
Impact Score: 6.4
Exploitability Score: 10
Severity: HIGH
Base Score: 9.8
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Impact Score: 5.9
Exploitability Score: 3.9
Severity: CRITICAL