CVE-2021-20317

Severity: medium (CVSS 4.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-09-27 · updated 2026-06-17
Weakness: CWE-665

Description

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.

Affected products

Debian Linux: 9.0, 10.0
Linux kernel: before 5.4; 5.4 — fixed in 5.4

How to fix

Upgrade to a fixed version: Linux kernel 5.4. Check the vendor advisory for mitigations.

References

https://bugzilla.redhat.com/show_bug.cgi?id=2005258
https://cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf
https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=511885d7061eda3eb1faf3f57dcc936ff75863f1
https://lists.debian.org/debian-lts-announce/2021/12/msg00012.html
https://lists.debian.org/debian-lts-announce/2022/03/msg00012.html
https://www.debian.org/security/2022/dsa-5096
https://bugzilla.redhat.com/show_bug.cgi?id=2005258
https://cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf
https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=511885d7061eda3eb1faf3f57dcc936ff75863f1
https://lists.debian.org/debian-lts-announce/2021/12/msg00012.html
https://lists.debian.org/debian-lts-announce/2022/03/msg00012.html
https://www.debian.org/security/2022/dsa-5096

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