medium 4.4

CVE-2021-20317 json

A flaw was found in the Linux kernel.

published 2021-09-27 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-7742

cvss: 4.4; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.4%; EPSS 0.4% chance of exploitation in 30 days, percentile 32%
public exploits: 0; none known

A flaw was found in the Linux kernel. A corrupted timer tree caused the task wakeup to be missing in the timerqueue_add function in lib/timerqueue.c. This flaw allows a local attacker with special user privileges to cause a denial of service, slowing and eventually stopping the system while running OSP.

Patch / fix

fixed in 1 distros 4 links 1

linux linux_kernel 5.4

debian ubuntu red hat rocky linux

linux Debian 14, Debian 13, Debian 12 5.4.6-1

debian advisories DEBIAN-CVE-2021-20317

linux Ubuntu 18.04 LTS 4.15.0-166.174
linux-aws Ubuntu 18.04 LTS 4.15.0-1118.125
linux-kvm Ubuntu 18.04 LTS 4.15.0-1105.107
linux-oracle Ubuntu 18.04 LTS 4.15.0-1085.93
linux-raspi2 Ubuntu 18.04 LTS 4.15.0-1101.108
linux-dell300x Ubuntu 18.04 LTS 4.15.0-1033.38
linux-gcp-4.15 Ubuntu 18.04 LTS 4.15.0-1114.128
linux-azure-4.15 Ubuntu 18.04 LTS 4.15.0-1129.142

ubuntu advisories UBUNTU-CVE-2021-20317

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-rt RHEL 8 4.18.0-348.2.1.rt7.132.el8_5
kernel-rt-kvm RHEL 8 4.18.0-348.2.1.rt7.132.el8_5
kernel-rt-core RHEL 8 4.18.0-348.2.1.rt7.132.el8_5
kernel-rt-modules RHEL 8 4.18.0-348.2.1.rt7.132.el8_5
kernel-rt-debug-kvm RHEL 8 4.18.0-348.2.1.rt7.132.el8_5
kernel-rt-debug-core RHEL 8 4.18.0-348.2.1.rt7.132.el8_5
kernel-rt-debug-modules RHEL 8 4.18.0-348.2.1.rt7.132.el8_5
kernel-rt-modules-extra RHEL 8 4.18.0-348.2.1.rt7.132.el8_5

red hat advisories RHSA-2021:4875 RHSA-2021:4871 RHSA-2021:4646 RHSA-2021:4647 RHSA-2021:4648 RHSA-2021:4650

kernel Rocky Linux 8 4.18.0-348.2.1.el8_5
kernel-rt Rocky Linux 8 4.18.0-348.2.1.rt7.132.el8_5

rocky linux advisories RLSA-2021:4647 RLSA-2021:4646

git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=511885d706… commit

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-2021-20317 updated 2026-11-07 cvss 4.4

kernel: timer tree corruption leads to missing wakeup and system freeze

Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
affected: workaround, no fix planned “Will not fix”
Red Hat CodeReady Linux Builder (v. 8) kernel-debuginfo-common-x86_64 4.18.0-348.2.1.el8_5, kernel-debuginfo-common-aarch64 4.18.0-348.2.1.el8_5, kernel-debuginfo-common-ppc64le 4.18.0-348.2.1.el8_5
fixed: vendor fix RHSA-2021:4647
Red Hat CodeReady Linux Builder EUS (v. 8.2) kernel-debuginfo-common-x86_64 4.18.0-193.70.1.el8_2, kernel-debuginfo-common-aarch64 4.18.0-193.70.1.el8_2, kernel-debuginfo-common-ppc64le 4.18.0-193.70.1.el8_2
fixed: vendor fix RHSA-2021:4871
Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-348.2.1.el8_5, kernel 4.18.0-348.2.1.el8_5, bpftool 4.18.0-348.2.1.el8_5, kernel-core 4.18.0-348.2.1.el8_5, kernel-tools 4.18.0-348.2.1.el8_5, python3-perf 4.18.0-348.2.1.el8_5, +15 more
fixed: vendor fix RHSA-2021:4647
Red Hat Enterprise Linux BaseOS EUS (v. 8.2) perf 4.18.0-193.70.1.el8_2, kernel 4.18.0-193.70.1.el8_2, bpftool 4.18.0-193.70.1.el8_2, kernel-core 4.18.0-193.70.1.el8_2, kernel-tools 4.18.0-193.70.1.el8_2, python3-perf 4.18.0-193.70.1.el8_2, +15 more
fixed: vendor fix RHSA-2021:4871
Red Hat Enterprise Linux BaseOS EUS (v.8.4) perf 4.18.0-305.28.1.el8_4, kernel 4.18.0-305.28.1.el8_4, bpftool 4.18.0-305.28.1.el8_4, kernel-core 4.18.0-305.28.1.el8_4, kernel-tools 4.18.0-305.28.1.el8_4, python3-perf 4.18.0-305.28.1.el8_4, +15 more Red Hat Enterprise Linux CRB EUS (v.8.4) kernel-debuginfo-common-x86_64 4.18.0-305.28.1.el8_4, kernel-debuginfo-common-aarch64 4.18.0-305.28.1.el8_4, kernel-debuginfo-common-ppc64le 4.18.0-305.28.1.el8_4
fixed: vendor fix RHSA-2021:4650
Red Hat Enterprise Linux for Real Time (v. 8) kernel-rt 4.18.0-348.2.1.rt7.132.el8_5, kernel-rt-core 4.18.0-348.2.1.rt7.132.el8_5, kernel-rt-modules 4.18.0-348.2.1.rt7.132.el8_5, kernel-rt-debug-core 4.18.0-348.2.1.rt7.132.el8_5, kernel-rt-debug-modules 4.18.0-348.2.1.rt7.132.el8_5, kernel-rt-modules-extra 4.18.0-348.2.1.rt7.132.el8_5, +2 more
fixed: vendor fix RHSA-2021:4646
Red Hat Enterprise Linux NFV EUS (v.8.4) kernel-rt 4.18.0-305.28.1.rt7.100.el8_4, kernel-rt-kvm 4.18.0-305.28.1.rt7.100.el8_4, kernel-rt-core 4.18.0-305.28.1.rt7.100.el8_4, kernel-rt-modules 4.18.0-305.28.1.rt7.100.el8_4, kernel-rt-debug-kvm 4.18.0-305.28.1.rt7.100.el8_4, kernel-rt-debug-core 4.18.0-305.28.1.rt7.100.el8_4, +4 more
fixed: vendor fix RHSA-2021:4648

show 5 more

Red Hat Enterprise Linux Real Time EUS (v. 8.2) kernel-rt 4.18.0-193.70.1.rt13.120.el8_2, kernel-rt-core 4.18.0-193.70.1.rt13.120.el8_2, kernel-rt-modules 4.18.0-193.70.1.rt13.120.el8_2, kernel-rt-debug-core 4.18.0-193.70.1.rt13.120.el8_2, kernel-rt-debug-modules 4.18.0-193.70.1.rt13.120.el8_2, kernel-rt-modules-extra 4.18.0-193.70.1.rt13.120.el8_2, +2 more
fixed: vendor fix RHSA-2021:4875
Red Hat Enterprise Linux Real Time for NFV (v. 8) kernel-rt 4.18.0-348.2.1.rt7.132.el8_5, kernel-rt-kvm 4.18.0-348.2.1.rt7.132.el8_5, kernel-rt-core 4.18.0-348.2.1.rt7.132.el8_5, kernel-rt-modules 4.18.0-348.2.1.rt7.132.el8_5, kernel-rt-debug-kvm 4.18.0-348.2.1.rt7.132.el8_5, kernel-rt-debug-core 4.18.0-348.2.1.rt7.132.el8_5, +4 more
fixed: vendor fix RHSA-2021:4646
Red Hat Enterprise Linux Real Time for NFV EUS (v. 8.2) kernel-rt 4.18.0-193.70.1.rt13.120.el8_2, kernel-rt-kvm 4.18.0-193.70.1.rt13.120.el8_2, kernel-rt-core 4.18.0-193.70.1.rt13.120.el8_2, kernel-rt-modules 4.18.0-193.70.1.rt13.120.el8_2, kernel-rt-debug-kvm 4.18.0-193.70.1.rt13.120.el8_2, kernel-rt-debug-core 4.18.0-193.70.1.rt13.120.el8_2, +4 more
fixed: vendor fix RHSA-2021:4875
Red Hat Enterprise Linux RT EUS (v.8.4) kernel-rt 4.18.0-305.28.1.rt7.100.el8_4, kernel-rt-core 4.18.0-305.28.1.rt7.100.el8_4, kernel-rt-modules 4.18.0-305.28.1.rt7.100.el8_4, kernel-rt-debug-core 4.18.0-305.28.1.rt7.100.el8_4, kernel-rt-debug-modules 4.18.0-305.28.1.rt7.100.el8_4, kernel-rt-modules-extra 4.18.0-305.28.1.rt7.100.el8_4, +2 more
fixed: vendor fix RHSA-2021:4648
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 9 rv, perf, rtla, kernel, bpftool, libperf, +82 more
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

cisa ICSA-22-167-09 updated 2022-06-14 cvss 4.4

Siemens SCALANCE LPE9403 Third-Party Vulnerabilities

Siemens SCALANCE LPE9403 <V2.0
affected: fixed in V2.0 support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

0.38% chance of exploitation in the next 30 days, higher than 32% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
NVD	3.1	4.4	CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
NVD	2.0	4.9	AV:L/AC:L/Au:N/C:N/I:N/A:C

Affected products

n/a kernel

Classification

Weakness

CWE-665 Improper Initialization

Technology feeds

Linux kernel rss critical rss

References

git.kernel.org /pub/scm/linux/kernel/git/tip/tip.git/commit/?id=511885d7061eda3eb1faf3f57dcc936ff75863f1
patch, vendor-advisory
debian.org /security/2022/dsa-5096
vendor-advisory, third-party-advisory
bugzilla.redhat.com /show_bug.cgi?id=2005258
issue-tracking, third-party-advisory
lists.debian.org /debian-lts-announce/2021/12/msg00012.html
mailing-list, third-party-advisory
lists.debian.org /debian-lts-announce/2022/03/msg00012.html
mailing-list, third-party-advisory
cert-portal.siemens.com /productcert/pdf/ssa-222547.pdf

Sources

CVE List CVE-2021-20317
NVD CVE-2021-20317

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.

Summary