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Fencer Vulns
medium 4.7

CVE-2025-68214 json

timers: Fix NULL function pointer race in timer_shutdown_sync()

published 2025-12-16 10 mo ago modified 2026-11-05 3 d ago also EUVD-2025-203682

cvss
4.7
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:

timers: Fix NULL function pointer race in timer_shutdown_sync()

There is a race condition between timer_shutdown_sync() and timer expiration that can lead to hitting a WARN_ON in expire_timers().

The issue occurs when timer_shutdown_sync() clears the timer function to NULL while the timer is still running on another CPU. The race scenario looks like this:

CPU0 CPU1 <SOFTIRQ> lock_timer_base() expire_timers() base->running_timer = timer; unlock_timer_base() [call_timer_fn enter] mod_timer() ... timer_shutdown_sync() lock_timer_base() // For now, will not detach the timer but only clear its function to NULL if (base->running_timer != timer) ret = detach_if_pending(timer, base, true); if (shutdown) timer->function = NULL; unlock_timer_base() [call_timer_fn exit] lock_timer_base() base->running_timer = NULL; unlock_timer_base() ... // Now timer is pending while its function set to NULL. // next timer trigger <SOFTIRQ> expire_timers() WARN_ON_ONCE(!fn) // hit ... lock_timer_base() // Now timer will detach if (base->running_timer != timer) ret = detach_if_pending(timer, base, true); if (shutdown) timer->function = NULL; unlock_timer_base()

The problem is that timer_shutdown_sync() clears the timer function regardless of whether the timer is currently running. This can leave a pending timer with a NULL function pointer, which triggers the WARN_ON_ONCE(!fn) check in expire_timers().

Fix this by only clearing the timer function when actually detaching the timer. If the timer is running, leave the function pointer intact, which is safe because the timer will be properly detached when it finishes running.

Patch / fix

  • Linux Linux 6.1.159, 6.6.118, 6.12.60, 6.17.10, 6.18
  • linux Debian 12 6.1.159-1
  • linux Debian 13 6.12.63-1
  • linux Debian 14 6.17.10-1

debian advisories DEBIAN-CVE-2025-68214

  • linux Ubuntu 22.04 LTS 5.15.0-185.195
  • linux Ubuntu 24.04 LTS 6.8.0-106.106
  • linux Ubuntu 25.10 6.17.0-19.19
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1111.118
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1050.53
  • linux-aws Ubuntu 25.10 6.17.0-1009.9
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1111.121
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1052.55

ubuntu advisories UBUNTU-CVE-2025-68214

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 6.12.0-211.43.1.el10_2
  • rv RHEL 10.2 6.12.0-211.43.1.el10_2
  • perf RHEL 10.2 6.12.0-211.43.1.el10_2
  • rtla RHEL 10.2 6.12.0-211.43.1.el10_2
  • libperf RHEL 10.2 6.12.0-211.43.1.el10_2
  • kernel-rt RHEL 10.2 6.12.0-211.43.1.el10_2
  • kernel-64k RHEL 10.2 6.12.0-211.43.1.el10_2
  • kernel-core RHEL 10.2 6.12.0-211.43.1.el10_2

red hat advisories RHSA-2026:49871RHSA-2026:49870

  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.81.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.81.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1.150700.17.45.1

suse advisories SUSE-SU-2026:4254-1SUSE-SU-2026:4369-1SUSE-SU-2026:23887-1SUSE-SU-2026:23902-1SUSE-SU-2026:23897-1SUSE-SU-2026:23881-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.38.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.38.1

opensuse advisories openSUSE-SU-2026:21910-1

  • kernel AlmaLinux 9 5.14.0-687.34.1.el9_8
  • rv AlmaLinux 9 5.14.0-687.34.1.el9_8
  • perf AlmaLinux 9 5.14.0-687.34.1.el9_8
  • rtla AlmaLinux 9 5.14.0-687.34.1.el9_8
  • libperf AlmaLinux 9 5.14.0-687.34.1.el9_8
  • kernel-rt AlmaLinux 9 5.14.0-687.34.1.el9_8
  • kernel-64k AlmaLinux 9 5.14.0-687.34.1.el9_8
  • kernel-core AlmaLinux 9 5.14.0-687.34.1.el9_8

almalinux advisories ALSA-2026:49870ALSA-2026:49871

  • kernel Rocky Linux 10 6.12.0-211.43.1.el10_2
  • kernel Rocky Linux 9 5.14.0-687.34.1.el9_8
  • kernel Rocky Linux 9 5.14.0-687.34.1.el9_8.cloud.1.0

rocky linux advisories RLSA-2026:49871RLSA-2026:49870RXSA-2026:49870

  • kernel Azure Linux 3.0 6.6.119.3-1

azure linux advisories AZL-72475

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-2025-68214 updated cvss 5.5

kernel: Linux kernel: Denial of Service due to NULL function pointer race in timer shutdown

  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.34.1.el9_8, perf 5.14.0-687.34.1.el9_8, rtla 5.14.0-687.34.1.el9_8, python3-perf 5.14.0-687.34.1.el9_8, kernel-devel-matched 5.14.0-687.34.1.el9_8, kernel-64k-devel-matched 5.14.0-687.34.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:49870
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.43.1.el10_2, perf 6.12.0-211.43.1.el10_2, rtla 6.12.0-211.43.1.el10_2, python3-perf 6.12.0-211.43.1.el10_2, kernel-devel-matched 6.12.0-211.43.1.el10_2, kernel-64k-devel-matched 6.12.0-211.43.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:49871
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.34.1.el9_8, kernel-64k 5.14.0-687.34.1.el9_8, kernel-core 5.14.0-687.34.1.el9_8, kernel-tools 5.14.0-687.34.1.el9_8, kernel-modules 5.14.0-687.34.1.el9_8, kernel-64k-core 5.14.0-687.34.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:49870
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.43.1.el10_2, kernel-64k 6.12.0-211.43.1.el10_2, kernel-core 6.12.0-211.43.1.el10_2, kernel-tools 6.12.0-211.43.1.el10_2, kernel-modules 6.12.0-211.43.1.el10_2, kernel-64k-core 6.12.0-211.43.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:49871
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.34.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.34.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.34.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.34.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.34.1.el9_8
    fixed: vendor fix RHSA-2026:49870
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.43.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.43.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.43.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.43.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.43.1.el10_2
    fixed: vendor fix RHSA-2026:49871
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.34.1.el9_8, kernel-rt-64k 5.14.0-687.34.1.el9_8, kernel-rt-core 5.14.0-687.34.1.el9_8, kernel-rt-modules 5.14.0-687.34.1.el9_8, kernel-rt-64k-core 5.14.0-687.34.1.el9_8, kernel-rt-debug-core 5.14.0-687.34.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:49870
show 4 more
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.43.1.el10_2, kernel-rt-64k 6.12.0-211.43.1.el10_2, kernel-rt-core 6.12.0-211.43.1.el10_2, kernel-rt-modules 6.12.0-211.43.1.el10_2, kernel-rt-64k-core 6.12.0-211.43.1.el10_2, kernel-rt-debug-core 6.12.0-211.43.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:49871
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.34.1.el9_8, kernel-rt-core 5.14.0-687.34.1.el9_8, kernel-rt-modules 5.14.0-687.34.1.el9_8, kernel-rt-debug-core 5.14.0-687.34.1.el9_8, kernel-rt-modules-core 5.14.0-687.34.1.el9_8, kernel-rt-debug-modules 5.14.0-687.34.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:49870
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.43.1.el10_2, kernel-rt-core 6.12.0-211.43.1.el10_2, kernel-rt-modules 6.12.0-211.43.1.el10_2, kernel-rt-debug-core 6.12.0-211.43.1.el10_2, kernel-rt-modules-core 6.12.0-211.43.1.el10_2, kernel-rt-debug-modules 6.12.0-211.43.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:49871
  • 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 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 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 SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 d ago

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 4.7 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
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.