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NVD / CVE Program· CNA Linux

CVE-2025-68214: timers: Fix NULL function pointer race in timer_shutdown_sync()

MediumCVSS 4.7 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 18/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.12% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: Linux Linux 176725f4848376530a0f0da9023f956afcc33585, 1a975716cc8977f461e45e28e3e5977d46ad7a6a, 20739af07383e6eb1ec59dcd70b72ebfa9ac362c; azl3 kernel 6.6.117.1-1 on Azure Linux 3.0 6.6.119.3-1.

Low priority for now. Upgrade to Linux Linux 176725f4848376530a0f0da9023f956afcc33585, 1a975716cc8977f461e45e28e3e5977d46ad7a6a, 20739af07383e6eb1ec59dcd70b72ebfa9ac362c; azl3 kernel 6.6.117.1-1 on Azure Linux 3.0 6.6.119.3-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published
Dec 16, 2025
Updated
Nov 5, 2026
EPSS
0.1% · 2th percentile

Report tools

JSON

Action score

18

Monitor

Low priority for now.

CVSS
18 / 40 · 4.7 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 6.2affected
    • debbcf812d735003c96c5e5968a3cfa4e1fbd1af and later · before ba43ac025c4318241f8edf94f31d2eebab86991baffected · git
    • 334c33aa487be406a149c8b87c38c8399d2dba8d and later · before 1a975716cc8977f461e45e28e3e5977d46ad7a6aaffected · git
    • 0cc04e80458a822300b93f82ed861a513edde194 and later · before 6665fbd7730b26d770c232b20d1b907e6a67a914affected · git
    • 0cc04e80458a822300b93f82ed861a513edde194 and later · before 176725f4848376530a0f0da9023f956afcc33585affected · git
    • 0cc04e80458a822300b93f82ed861a513edde194 and later · before a01efa7a780c42ac5170a949bd95c9786ffcc60aaffected · git
    • 0cc04e80458a822300b93f82ed861a513edde194 and later · before 20739af07383e6eb1ec59dcd70b72ebfa9ac362caffected · git
    • 6.1.158 and later · before 6.1.159affected · semver
    • before 6.2not affected · semver
    • 6.1.159 and later · up to and including 6.1.*not affected · semver
Affected versions · NVD (5)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel6.2 and later · before 6.6.118
  • linux linux kernel6.7 and later · before 6.12.60
  • linux linux kernel6.13 and later · before 6.17.10
  • linux linux kernel6.1.158
  • linux linux kernel6.18

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:10kernelbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64kbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64k-corebefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64k-debugbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64k-debug-corebefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64k-debug-develbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64k-debug-devel-matchedbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64k-debug-modulesbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-corebefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-extrabefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64k-develbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64k-devel-matchedbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64k-modulesbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64k-modules-corebefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-64k-modules-extrabefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-abi-stablelistsbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-corebefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-cross-headersbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-debugbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-debug-corebefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-debug-develbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-debug-devel-matchedbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-debug-modulesbefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2
AlmaLinux:10kernel-debug-modules-corebefore 6.12.0-211.43.1.el10_26.12.0-211.43.1.el10_2

+96

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
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  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe…KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2025-40251Dec 4, 2025 · devlink: rate: Unset parent pointer in devl_rate_nodes_destroy
    22Monitor
  • ← EarlierCVE-2025-68211Dec 16, 2025 · ksm: use range-walk function to jump over holes in scan_get_next_rmap_item
    22Monitor
  • Later →CVE-2025-68223Dec 16, 2025 · drm/radeon: delete radeon_fence_process in is_signaled, no deadlock
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux176725f4848376530a0f0da9023f956afcc33585Vendor (CNA)
Linux Linux1a975716cc8977f461e45e28e3e5977d46ad7a6aVendor (CNA)
Linux Linux20739af07383e6eb1ec59dcd70b72ebfa9ac362cVendor (CNA)
Linux Linux6.1.159Vendor (CNA)
Linux Linux6665fbd7730b26d770c232b20d1b907e6a67a914Vendor (CNA)
Linux Linuxa01efa7a780c42ac5170a949bd95c9786ffcc60aVendor (CNA)
Linux Linuxba43ac025c4318241f8edf94f31d2eebab86991bVendor (CNA)
azl3 kernel 6.6.117.1-1 on Azure Linux 3.06.6.119.3-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
almalinux:kernel5.14.0-687.34.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k5.14.0-687.34.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-core5.14.0-687.34.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug5.14.0-687.34.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-core5.14.0-687.34.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel5.14.0-687.34.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel-matched5.14.0-687.34.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules5.14.0-687.34.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-core5.14.0-687.34.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-extra5.14.0-687.34.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel5.14.0-687.34.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel-matched5.14.0-687.34.1.el9_8 · AlmaLinux:9Package registry (OSV)
debian:linux6.1.159-1 · Debian:12Package registry (OSV)
opensuse:dtb-aarch646.12.0-160000.38.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-64kb6.12.0-160000.38.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-azure6.12.0-160000.38.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-default6.12.0-160000.38.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-default-base6.12.0-160000.38.1.160000.2.22 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-docs6.12.0-160000.38.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-kvmsmall6.12.0-160000.38.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-obs-build6.12.0-160000.38.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-obs-qa6.12.0-160000.38.1 · openSUSE:Leap 16.0Package registry (OSV)

+34

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-362 · Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

References

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records