CVE-2025-21701 – This CVE describes a race condition vulnerabili... (How to Fix)

Q: What is the severity of CVE-2025-21701?

CVE-2025-21701 has a CVSS score of 4.7 (MEDIUM). This CVE describes a race condition vulnerability in the Linux kernel's network subsystem where device unregistration can conflict with ethtool operations, potentially causing kernel warnings or crashes. It affects Linux systems where network devices are being modified via ethtool while simultaneously being unregistered. The vulnerability requires local access to trigger.

📋 TL;DR

This CVE describes a race condition vulnerability in the Linux kernel's network subsystem where device unregistration can conflict with ethtool operations, potentially causing kernel warnings or crashes. It affects Linux systems where network devices are being modified via ethtool while simultaneously being unregistered. The vulnerability requires local access to trigger.

💻 Affected Systems

Products:

Linux Kernel

Versions: Versions up to and including 6.13.0-rc6

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires ethtool access and concurrent device unregistration operations.

📦 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 →

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 leading to denial of service, potentially disrupting network connectivity on affected systems.

🟠

Likely Case

Kernel warning messages in system logs and possible temporary disruption of ethtool operations on the affected network interface.

🟢

If Mitigated

Minor performance impact or failed ethtool operations with proper error handling.

🌐 Internet-Facing: LOW - Requires local access to trigger, not remotely exploitable.

🏢 Internal Only: MEDIUM - Local users or processes with ethtool access could cause system instability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires race condition timing and local access to trigger. Primarily a stability issue rather than a security bypass.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Fixed in kernel commits 12e070eb6964b341b41677fd260af5a305316a1f and later

Vendor Advisory: https://git.kernel.org/stable/c/12e070eb6964b341b41677fd260af5a305316a1f

Restart Required: Yes

Instructions:

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

🔧 Temporary Workarounds

Restrict ethtool access

linux

Limit which users can run ethtool commands to reduce attack surface

chmod 750 /sbin/ethtool
setcap -r /sbin/ethtool

Avoid concurrent operations

linux

Ensure network device configuration changes and unregistration don't occur simultaneously

🧯 If You Can't Patch

Implement strict access controls on ethtool binary
Monitor system logs for kernel warnings related to mutex or device unregistration

🔍 How to Verify

Check if Vulnerable:

Check kernel version: uname -r and compare to affected versions up to 6.13.0-rc6

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version is newer than affected versions and check git commit contains the fix

📡 Detection & Monitoring

Log Indicators:

Kernel warnings about mutex magic mismatch
DEBUG_LOCKS_WARN_ON messages in dmesg
ethtool-related crash reports

Network Indicators:

Unusual network interface state changes

SIEM Query:

source="kernel" AND ("DEBUG_LOCKS_WARN_ON" OR "mutex magic" OR "ethtool" AND "warning")

📊 Metadata

CVE ID: CVE-2025-21701

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: 0.03% exploit probability (8.8th percentile)

Published: February 13, 2025

Last Updated: November 3, 2025

🔗 References

📤 Share & Export

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🔗 Related Vulnerabilities

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