CVE-2025-68214 – A race condition in the Linux kernel's timer

Q: What is the severity of CVE-2025-68214?

CVE-2025-68214 has a CVSS score of 4.7 (MEDIUM). A race condition in the Linux kernel's timer_shutdown_sync() function can cause a kernel warning (WARN_ON) when a timer's function pointer is cleared to NULL while the timer is still executing on another CPU. This affects all Linux systems using vulnerable kernel versions. The vulnerability can lead to kernel instability but not direct privilege escalation.

📋 TL;DR

A race condition in the Linux kernel's timer_shutdown_sync() function can cause a kernel warning (WARN_ON) when a timer's function pointer is cleared to NULL while the timer is still executing on another CPU. This affects all Linux systems using vulnerable kernel versions. The vulnerability can lead to kernel instability but not direct privilege escalation.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific affected versions not explicitly stated in CVE; likely affects multiple stable kernel versions before the fix commits.

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: All Linux systems using the affected timer subsystem code are vulnerable regardless of configuration.

📦 What is this software?

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic or system crash due to triggered WARN_ON leading to denial of service, potentially disrupting critical services.

🟠

Likely Case

Kernel warning messages in system logs and possible system instability or crashes under specific timing conditions.

🟢

If Mitigated

Minor system logging with no significant impact if warnings are handled gracefully by the system.

🌐 Internet-Facing: LOW - This is a local kernel race condition not directly exploitable via network vectors.

🏢 Internal Only: MEDIUM - Local users or processes could potentially trigger the race condition, causing system instability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: HIGH - Requires precise timing to trigger the race condition between CPU cores.

Exploitation requires local access and ability to manipulate kernel timers with specific timing.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits: 176725f4848376530a0f0da9023f956afcc33585, 1a975716cc8977f461e45e28e3e5977d46ad7a6a, 20739af07383e6eb1ec59dcd70b72ebfa9ac362c, 6665fbd7730b26d770c232b20d1b907e6a67a914, a01efa7a780c42ac5170a949bd95c9786ffcc60a

Vendor Advisory: https://git.kernel.org/stable/c/

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. Check with your distribution for specific patched kernel packages. 3. Reboot system after kernel update.

🔧 Temporary Workarounds

No effective workaround

linux

This is a kernel-level race condition that cannot be mitigated without patching.

🧯 If You Can't Patch

Monitor system logs for kernel warnings related to timer_shutdown_sync() or expire_timers()
Implement system redundancy and failover mechanisms to maintain availability if crashes occur

🔍 How to Verify

Check if Vulnerable:

Check kernel version and compare with patched versions from kernel git repository. Look for kernel warnings in dmesg or system logs.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes the fix commits. Monitor system logs for absence of WARN_ON messages related to timer functions.

📡 Detection & Monitoring

Log Indicators:

Kernel WARN_ON messages mentioning expire_timers(), timer_shutdown_sync(), or NULL function pointer

SIEM Query:

source="kernel" AND ("WARN_ON" OR "expire_timers" OR "timer_shutdown_sync")

📊 Metadata

CVE ID: CVE-2025-68214

CVSS v3 Score: 4.7 (MEDIUM)

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

CWE: CWE-362

EPSS Score: 0.05% exploit probability (15.6th percentile)

Published: December 16, 2025

Last Updated: February 26, 2026

🔗 References

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🔗 Related Vulnerabilities

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