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Fencer Vulns
high 8.1

CVE-2018-20836 json

An issue was discovered in the Linux kernel before 4.20.

published 2019-05-07 7 y ago modified 2026-06-17 4 mo ago also EUVD-2018-13376

cvss
8.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
5.1%
EPSS 5.1% chance of exploitation in 30 days, percentile 92%
public exploits
0
none known

Summary

An issue was discovered in the Linux kernel before 4.20. There is a race condition in smp_task_timedout() and smp_task_done() in drivers/scsi/libsas/sas_expander.c, leading to a use-after-free.

Patch / fix

  • linux linux_kernel 3.16.72, 3.18.140, 4.4.180, 4.9.175, 4.14.118, 4.19.42
  • linux Debian 14, Debian 13, Debian 12 5.2.6-1

debian advisories DEBIAN-CVE-2018-20836

  • linux Ubuntu 16.04 LTS 4.4.0-157.185
  • linux Ubuntu 18.04 LTS 4.15.0-44.47
  • linux-aws Ubuntu 16.04 LTS 4.4.0-1090.101
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1032.34
  • linux-gcp Ubuntu 16.04 LTS 4.15.0-1027.28~16.04.1
  • linux-gcp Ubuntu 18.04 LTS 4.15.0-1027.28
  • linux-hwe Ubuntu 16.04 LTS 4.15.0-45.48~16.04.1
  • linux-hwe Ubuntu 18.04 LTS 4.18.0-14.15~18.04.1

ubuntu advisories UBUNTU-CVE-2018-20836

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 7 3.10.0-1160.el7
  • perf RHEL 7 3.10.0-1160.el7
  • bpftool RHEL 7 3.10.0-1160.el7
  • python-perf RHEL 7 3.10.0-1160.el7
  • kernel-kdump RHEL 7 3.10.0-1160.el7
  • kernel-tools RHEL 7 3.10.0-1160.el7
  • kernel-tools-libs RHEL 7 3.10.0-1160.el7
  • kernel-bootwrapper RHEL 7 3.10.0-1160.el7

red hat advisories RHSA-2020:4060RHSA-2020:4062RHSA-2020:5656RHSA-2021:0019

  • kernel-syms SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.20.1
  • kernel-source SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.20.1
  • kernel-default SLES for SAP 12 SP5, SLES 12 SP5, SLE Workstation Extension 12 SP5 +2 more 4.12.14-122.20.1
  • kernel-obs-build SLE Software Development Kit 12 SP5 4.12.14-122.20.1
  • kernel-azure SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-16.13.1
  • kernel-syms-azure SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-16.13.1
  • kernel-source-azure SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-16.13.1
  • kernel-rt SLE Real Time 12 SP5 4.12.14-10.8.1

suse advisories SUSE-SU-2020:1142-1SUSE-SU-2020:1118-1SUSE-SU-2020:1084-1SUSE-SU-2019:2450-1SUSE-SU-2019:2430-1SUSE-SU-2019:2069-1

  • kernel-syms openSUSE Leap 15.1 4.12.14-lp151.28.10.1
  • kernel-obs-qa openSUSE Leap 15.1 4.12.14-lp151.28.10.1
  • kernel-source openSUSE Leap 15.1 4.12.14-lp151.28.10.1
  • kernel-default openSUSE Leap 15.1 4.12.14-lp151.28.10.1
  • kernel-vanilla openSUSE Leap 15.1 4.12.14-lp151.28.10.1
  • kernel-kvmsmall openSUSE Leap 15.1 4.12.14-lp151.28.10.1
  • kernel-obs-build openSUSE Leap 15.1 4.12.14-lp151.28.10.1
  • kernel-syms openSUSE Leap 15.0 4.12.14-lp150.12.67.1

opensuse advisories openSUSE-SU-2019:1757-1openSUSE-SU-2019:1716-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2018-20836 updated cvss 7.0

kernel: race condition in smp_task_timedout() and smp_task_done() in drivers/scsi/libsas/sas_expander.c leads to use-after-free

  • Red Hat Enterprise Linux 5 kernel Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, kernel-alt, python-perf, kernel-kdump, kernel-tools, +3 more
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise MRG 2 kernel-rt, mrg-rt-release, kernel-rt-trace, kernel-rt-vanilla, kernel-rt-firmware
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux Client (v. 7) perf 3.10.0-1160.el7, kernel 3.10.0-1160.el7, bpftool 3.10.0-1160.el7, python-perf 3.10.0-1160.el7, kernel-tools 3.10.0-1160.el7, kernel-tools-libs 3.10.0-1160.el7, +2 more Red Hat Enterprise Linux Client Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.el7 Red Hat Enterprise Linux ComputeNode (v. 7) perf 3.10.0-1160.el7, kernel 3.10.0-1160.el7, bpftool 3.10.0-1160.el7, python-perf 3.10.0-1160.el7, kernel-tools 3.10.0-1160.el7, kernel-tools-libs 3.10.0-1160.el7, +2 more
    fixed: vendor fix RHSA-2020:4060
  • Red Hat Enterprise Linux ComputeNode EUS (v. 7.6) perf 3.10.0-957.65.1.el7, kernel 3.10.0-957.65.1.el7, bpftool 3.10.0-957.65.1.el7, python-perf 3.10.0-957.65.1.el7, kernel-tools 3.10.0-957.65.1.el7, kernel-tools-libs 3.10.0-957.65.1.el7, +2 more
    fixed: vendor fix RHSA-2020:5656
  • Red Hat Enterprise Linux ComputeNode EUS (v. 7.7) perf 3.10.0-1062.43.1.el7, kernel 3.10.0-1062.43.1.el7, bpftool 3.10.0-1062.43.1.el7, python-perf 3.10.0-1062.43.1.el7, kernel-tools 3.10.0-1062.43.1.el7, kernel-tools-libs 3.10.0-1062.43.1.el7, +2 more
    fixed: vendor fix RHSA-2021:0019
  • Red Hat Enterprise Linux ComputeNode Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.el7
    fixed: vendor fix RHSA-2020:4060
  • Red Hat Enterprise Linux ComputeNode Optional EUS (v. 7.6) kernel-debuginfo-common-x86_64 3.10.0-957.65.1.el7
    fixed: vendor fix RHSA-2020:5656
  • Red Hat Enterprise Linux ComputeNode Optional EUS (v. 7.7) kernel-debuginfo-common-x86_64 3.10.0-1062.43.1.el7
    fixed: vendor fix RHSA-2021:0019
show 10 more
  • Red Hat Enterprise Linux for Real Time (v. 7) kernel-rt 3.10.0-1160.rt56.1131.el7, kernel-rt-trace 3.10.0-1160.rt56.1131.el7, kernel-rt-debuginfo-common-x86_64 3.10.0-1160.rt56.1131.el7 Red Hat Enterprise Linux for Real Time for NFV (v. 7) kernel-rt 3.10.0-1160.rt56.1131.el7, kernel-rt-kvm 3.10.0-1160.rt56.1131.el7, kernel-rt-trace 3.10.0-1160.rt56.1131.el7, kernel-rt-debug-kvm 3.10.0-1160.rt56.1131.el7, kernel-rt-trace-kvm 3.10.0-1160.rt56.1131.el7, kernel-rt-debuginfo-common-x86_64 3.10.0-1160.rt56.1131.el7
    fixed: vendor fix RHSA-2020:4062
  • Red Hat Enterprise Linux Server (v. 7) perf 3.10.0-1160.el7, kernel 3.10.0-1160.el7, bpftool 3.10.0-1160.el7, python-perf 3.10.0-1160.el7, kernel-kdump 3.10.0-1160.el7, kernel-tools 3.10.0-1160.el7, +7 more
    fixed: vendor fix RHSA-2020:4060
  • Red Hat Enterprise Linux Server EUS (v. 7.6) perf 3.10.0-957.65.1.el7, kernel 3.10.0-957.65.1.el7, bpftool 3.10.0-957.65.1.el7, python-perf 3.10.0-957.65.1.el7, kernel-kdump 3.10.0-957.65.1.el7, kernel-tools 3.10.0-957.65.1.el7, +7 more
    fixed: vendor fix RHSA-2020:5656
  • Red Hat Enterprise Linux Server EUS (v. 7.7) perf 3.10.0-1062.43.1.el7, kernel 3.10.0-1062.43.1.el7, bpftool 3.10.0-1062.43.1.el7, python-perf 3.10.0-1062.43.1.el7, kernel-kdump 3.10.0-1062.43.1.el7, kernel-tools 3.10.0-1062.43.1.el7, +7 more
    fixed: vendor fix RHSA-2021:0019
  • Red Hat Enterprise Linux Server Optional (v. 7) kernel-debuginfo-common-ppc64 3.10.0-1160.el7, kernel-debuginfo-common-x86_64 3.10.0-1160.el7, kernel-debuginfo-common-ppc64le 3.10.0-1160.el7
    fixed: vendor fix RHSA-2020:4060
  • Red Hat Enterprise Linux Server Optional EUS (v. 7.6) kernel-debuginfo-common-ppc64 3.10.0-957.65.1.el7, kernel-debuginfo-common-x86_64 3.10.0-957.65.1.el7, kernel-debuginfo-common-ppc64le 3.10.0-957.65.1.el7
    fixed: vendor fix RHSA-2020:5656
  • Red Hat Enterprise Linux Server Optional EUS (v. 7.7) kernel-debuginfo-common-ppc64 3.10.0-1062.43.1.el7, kernel-debuginfo-common-x86_64 3.10.0-1062.43.1.el7, kernel-debuginfo-common-ppc64le 3.10.0-1062.43.1.el7
    fixed: vendor fix RHSA-2021:0019
  • Red Hat Enterprise Linux Workstation (v. 7) perf 3.10.0-1160.el7, kernel 3.10.0-1160.el7, bpftool 3.10.0-1160.el7, python-perf 3.10.0-1160.el7, kernel-tools 3.10.0-1160.el7, kernel-tools-libs 3.10.0-1160.el7, +2 more Red Hat Enterprise Linux Workstation Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.el7
    fixed: vendor fix RHSA-2020:4060
  • Red Hat Virtualization 4.2 Hypervisor for RHEL 7.6 EUS perf 3.10.0-957.65.1.el7, python-perf 3.10.0-957.65.1.el7
    fixed: vendor fix RHSA-2020:5656
  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux ComputeNode EUS (v. 7.7) kernel-headers 3.10.0-1062.43.1.el7 Red Hat Enterprise Linux Server EUS (v. 7.7) kernel-headers 3.10.0-1062.43.1.el7
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

5.09% chance of exploitation in the next 30 days, higher than 92% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 9.3 AV:N/AC:M/Au:N/C:C/I:C/A:C

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
  • CWE-416 Use After Free
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.