CVE-2025-21975 – This CVE describes a NULL pointer dereference v... (How to Fix)

Q: What is the severity of CVE-2025-21975?

CVE-2025-21975 has a CVSS score of 5.5 (MEDIUM). This CVE describes a NULL pointer dereference vulnerability in the Linux kernel's mlx5 network driver. If exploited, it could cause a kernel panic or system crash on systems using Mellanox network adapters. The vulnerability affects Linux systems with the mlx5 driver loaded.

📋 TL;DR

This CVE describes a NULL pointer dereference vulnerability in the Linux kernel's mlx5 network driver. If exploited, it could cause a kernel panic or system crash on systems using Mellanox network adapters. The vulnerability affects Linux systems with the mlx5 driver loaded.

💻 Affected Systems

Products:

Linux kernel with mlx5 network driver

Versions: Specific kernel versions containing the vulnerable code (check git commits for exact ranges)

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems with Mellanox network hardware using the mlx5 driver. Requires the driver to be loaded and in use.

📦 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...

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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 leading to system crash and denial of service, potentially requiring physical access to reboot affected systems.

🟠

Likely Case

System crash or kernel panic causing temporary denial of service until system reboot.

🟢

If Mitigated

No impact if proper kernel hardening and privilege separation are in place, though system stability could still be affected.

🌐 Internet-Facing: LOW - This requires local access or ability to trigger specific network driver operations.

🏢 Internal Only: MEDIUM - Internal attackers with local access could potentially crash systems using affected network hardware.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access and ability to trigger specific network driver operations. Likely requires root or elevated privileges.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing the git commits referenced in the CVE

Vendor Advisory: https://git.kernel.org/stable/c/093b4aaec97ec048623e3fe1e516fc45a954d412

Restart Required: Yes

Instructions:

1. Update to a patched kernel version containing the fix commits. 2. Reboot the system to load the new kernel. 3. Verify the mlx5 driver is functioning correctly after reboot.

🔧 Temporary Workarounds

Unload mlx5 driver

linux

Remove the vulnerable driver module if Mellanox hardware is not required

sudo modprobe -r mlx5_core

Blacklist mlx5 driver

linux

Prevent the driver from loading at boot

echo 'blacklist mlx5_core' | sudo tee /etc/modprobe.d/blacklist-mlx5.conf

🧯 If You Can't Patch

Restrict local access to systems using affected hardware
Implement strict privilege separation and limit root access

🔍 How to Verify

Check if Vulnerable:

Check if mlx5 driver is loaded: lsmod | grep mlx5. Check kernel version against patched versions.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version is updated and mlx5 driver loads without errors in dmesg.

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages in /var/log/messages or dmesg
NULL pointer dereference errors related to mlx5

Network Indicators:

Sudden loss of network connectivity on Mellanox interfaces

SIEM Query:

search 'kernel panic' OR 'NULL pointer dereference' AND 'mlx5'

📊 Metadata

CVE ID: CVE-2025-21975

CVSS v3 Score: 5.5 (MEDIUM)

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

CWE: CWE-476

EPSS Score: 0.11% exploit probability (29.1th percentile)

Published: April 1, 2025

Last Updated: November 3, 2025

🔗 References

📤 Share & Export

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