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Fencer Vulns
medium 5.5

CVE-2026-23168 json

flex_proportions: make fprop_new_period() hardirq safe

published 2026-02-14 8 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-5870

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

flex_proportions: make fprop_new_period() hardirq safe

Bernd has reported a lockdep splat from flexible proportions code that is essentially complaining about the following race:

<timer fires> run_timer_softirq - we are in softirq context call_timer_fn writeout_period fprop_new_period write_seqcount_begin(&p->sequence);

<hardirq is raised> ... blk_mq_end_request() blk_update_request() ext4_end_bio() folio_end_writeback() __wb_writeout_add() __fprop_add_percpu_max() if (unlikely(max_frac < FPROP_FRAC_BASE)) { fprop_fraction_percpu() seq = read_seqcount_begin(&p->sequence); - sees odd sequence so loops indefinitely

Note that a deadlock like this is only possible if the bdi has configured maximum fraction of writeout throughput which is very rare in general but frequent for example for FUSE bdis. To fix this problem we have to make sure write section of the sequence counter is irqsafe.

Patch / fix

  • Linux Linux 6.1.162, 6.6.123, 6.12.69, 6.18.9, 6.19
  • linux Debian 12 6.1.162-1
  • linux Debian 13 6.12.69-1
  • linux Debian 14 6.18.9-1

debian advisories DEBIAN-CVE-2026-23168

  • linux Ubuntu 24.04 LTS 6.8.0-117.117
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1055.58
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1058.61
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1054.60
  • linux-ibm Ubuntu 24.04 LTS 6.8.0-1055.56
  • linux-azure Ubuntu 24.04 LTS 6.8.0-1056.62
  • linux-gkeop Ubuntu 24.04 LTS 6.8.0-1041.44
  • linux-raspi Ubuntu 24.04 LTS 6.8.0-1056.60

ubuntu advisories UBUNTU-CVE-2026-23168

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 10.2 6.12.0-211.37.1.el10_2
  • rv RHEL 10.2 6.12.0-211.37.1.el10_2
  • perf RHEL 10.2 6.12.0-211.37.1.el10_2
  • rtla RHEL 10.2 6.12.0-211.37.1.el10_2
  • libperf RHEL 10.2 6.12.0-211.37.1.el10_2
  • kernel-rt RHEL 10.2 6.12.0-211.37.1.el10_2
  • kernel-64k RHEL 10.2 6.12.0-211.37.1.el10_2
  • kernel-core RHEL 10.2 6.12.0-211.37.1.el10_2

red hat advisories RHSA-2026:42919

  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.55.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.55.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.55.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.55.1
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.55.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.55.1
  • kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.55.1
  • kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.55.1.150700.17.33.1

suse advisories SUSE-SU-2026:2238-1SUSE-SU-2026:21834-1

  • kernel AlmaLinux 10 6.12.0-211.37.1.el10_2
  • rv AlmaLinux 10 6.12.0-211.37.1.el10_2
  • perf AlmaLinux 10 6.12.0-211.37.1.el10_2
  • rtla AlmaLinux 10 6.12.0-211.37.1.el10_2
  • libperf AlmaLinux 10 6.12.0-211.37.1.el10_2
  • kernel-rt AlmaLinux 10 6.12.0-211.37.1.el10_2
  • kernel-64k AlmaLinux 10 6.12.0-211.37.1.el10_2
  • kernel-core AlmaLinux 10 6.12.0-211.37.1.el10_2

almalinux advisories ALSA-2026:42919

  • kernel Rocky Linux 10 6.12.0-211.37.1.el10_2

rocky linux advisories RLSA-2026:42919

  • kernel Azure Linux 3.0 6.6.126.1-1

azure linux advisories AZL-77733

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2026-23168 updated cvss 5.5

kernel: flex_proportions: make fprop_new_period() hardirq safe

  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.37.1.el10_2, perf 6.12.0-211.37.1.el10_2, rtla 6.12.0-211.37.1.el10_2, python3-perf 6.12.0-211.37.1.el10_2, kernel-devel-matched 6.12.0-211.37.1.el10_2, kernel-64k-devel-matched 6.12.0-211.37.1.el10_2, +7 more Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.37.1.el10_2, kernel-64k 6.12.0-211.37.1.el10_2, kernel-core 6.12.0-211.37.1.el10_2, kernel-tools 6.12.0-211.37.1.el10_2, kernel-modules 6.12.0-211.37.1.el10_2, kernel-64k-core 6.12.0-211.37.1.el10_2, +28 more Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.37.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.37.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.37.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.37.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.37.1.el10_2 Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.37.1.el10_2, kernel-rt-64k 6.12.0-211.37.1.el10_2, kernel-rt-core 6.12.0-211.37.1.el10_2, kernel-rt-modules 6.12.0-211.37.1.el10_2, kernel-rt-64k-core 6.12.0-211.37.1.el10_2, kernel-rt-debug-core 6.12.0-211.37.1.el10_2, +14 more Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.37.1.el10_2, kernel-rt-core 6.12.0-211.37.1.el10_2, kernel-rt-modules 6.12.0-211.37.1.el10_2, kernel-rt-debug-core 6.12.0-211.37.1.el10_2, kernel-rt-modules-core 6.12.0-211.37.1.el10_2, kernel-rt-debug-modules 6.12.0-211.37.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:42919
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 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

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

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.