kernel: infinite loop in update_blocked_averages() in kernel/sched/fair.c leading to denial of service
Published Feb 22, 2019
9.8
CRITICALCVSS 3.1
EPSS 4.17%
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
No data.
Configuration 1
- ≥ 4.13 · < 4.14.93
- ≥ 4.19 · < 4.19.15
- ≥ 4.20 · < 4.20.2
- 5.0
Configuration 2
- 14.04
- 16.04
- 18.04
Configuration 3
- 8.0
- 8
No data.
Red Hat Enterprise Linux 8
kernel-0:4.18.0-80.7.1.el8_0
Fixed · RHSA-2019:1959
Red Hat Enterprise Linux 8
kernel-rt-0:4.18.0-80.7.1.rt9.153.el8_0
Fixed · RHSA-2019:1971
Red Hat Enterprise Linux 5
kernel
Not affected
Red Hat Enterprise Linux 6
kernel
Not affected
Red Hat Enterprise Linux 7
kernel
Not affected
Red Hat Enterprise Linux 7
kernel-alt
Will not fix
Red Hat Enterprise Linux 7
kernel-rt
Not affected
Red Hat Enterprise MRG 2
kernel-rt
Not affected
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 8 | kernel-0:4.18.0-80.7.1.el8_0 | Fixed | RHSA-2019:1959 |
| Red Hat Enterprise Linux 8 | kernel-rt-0:4.18.0-80.7.1.rt9.153.el8_0 | Fixed | RHSA-2019:1971 |
| Red Hat Enterprise Linux 5 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 6 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel-alt | Will not fix | n/a |
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | n/a |
| Red Hat Enterprise MRG 2 | kernel-rt | Not affected | n/a |
No package ranges for this CVE.
Remediation
No remediation recorded yet.
Metrics
No CVSS v4.0 score for this CVE.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
AV:N/AC:L/Au:N/C:P/I:P/A:P
This CVE is not in the KEV list.
No CISA SSVC assessment for this CVE yet.
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 1, 2026.
Score over time
2021–2026- EPSS v1
- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Percentile over time
- EPSS v1
- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Table of values (17 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 1, 2026 | 4.17% (0.04173) | 90.59th | v5 (v2026.06.15) |
| Jun 15, 2026 | 4.17% (0.04173) | 89.57th | v5 (v2026.06.15) |
| Nov 21, 2025 | 0.73% (0.00730) | 71.94th | v4 (v2025.03.14) |
| Nov 18, 2025 | 6.26% (0.06261) | 89.99th | v4 (v2025.03.14) |
| Mar 17, 2025 | 0.69% (0.00691) | 70.14th | v4 (v2025.03.14) |
| Dec 12, 2024 | 1.46% (0.01461) | 87.25th | v3 (v2023.03.01) |
| Jul 15, 2024 | 1.46% (0.01461) | 86.83th | v3 (v2023.03.01) |
| Feb 16, 2024 | 1.31% (0.01309) | 85.50th | v3 (v2023.03.01) |
| Mar 7, 2023 | 1.06% (0.01061) | 81.88th | v3 (v2023.03.01) |
| Mar 6, 2023 | 1.54% (0.01537) | 74.52th | v2 (v2022.01.01) |
| Feb 23, 2023 | 1.54% (0.01537) | 74.48th | v2 (v2022.01.01) |
| Apr 1, 2022 | 1.54% (0.01537) | 72.41th | v2 (v2022.01.01) |
| Feb 4, 2022 | 1.54% (0.01537) | 51.33th | v2 (v2022.01.01) |
| Feb 3, 2022 | 2.57% (0.02567) | 55.02th | v1 |
| Jan 6, 2022 | 2.57% (0.02567) | 54.58th | v1 |
| Sep 1, 2021 | 2.57% (0.02567) | 78.88th | v1 |
| Apr 14, 2021 | 2.57% (0.02567) | 0.00th | v1 |
References (13)
- http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c40f7d74c741a907cfaeb73a7697081881c497d0 x_refsource_MISCPatchVendor Advisory
- https://access.redhat.com/errata/RHSA-2019:1959 vendor-advisoryx_refsource_REDHATThird Party Advisory
- https://access.redhat.com/errata/RHSA-2019:1971 vendor-advisoryx_refsource_REDHATThird Party Advisory
- https://access.redhat.com/security/cve/CVE-2018-20784 Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1680540 Issue Tracking
- https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.20.2 x_refsource_MISCRelease NotesVendor Advisory
- https://github.com/torvalds/linux/commit/c40f7d74c741a907cfaeb73a7697081881c497d0 x_refsource_MISCPatchThird Party Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2018-20784
- https://usn.ubuntu.com/4115-1/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://usn.ubuntu.com/4118-1/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://usn.ubuntu.com/4211-1/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://usn.ubuntu.com/4211-2/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://www.cve.org/CVERecord?id=CVE-2018-20784
Change history (0)
No recorded changes yet.