CVE-2025-38645 – A NULL pointer dereference vulnerability in the... (How to Fix)

Q: What is the severity of CVE-2025-38645?

CVE-2025-38645 has a CVSS score of 5.5 (MEDIUM). A NULL pointer dereference vulnerability in the Linux kernel's mlx5 network driver could cause kernel crashes when device memory allocation fails. This affects systems using Mellanox network adapters with vulnerable kernel versions. The vulnerability requires local access to trigger.

📋 TL;DR

A NULL pointer dereference vulnerability in the Linux kernel's mlx5 network driver could cause kernel crashes when device memory allocation fails. This affects systems using Mellanox network adapters with vulnerable kernel versions. The vulnerability requires local access to trigger.

💻 Affected Systems

Products:

Linux kernel mlx5 network driver

Versions: Specific vulnerable kernel versions referenced in the CVE links; typically affects multiple stable kernel branches.

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems with Mellanox network hardware using the mlx5 driver. Virtual environments with virtual Mellanox devices may also be affected.

📦 What is this software?

Debian Linux by Debian

View all CVEs affecting Debian Linux →

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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic leading to system crash and denial of service, potentially causing data loss or service disruption.

🟠

Likely Case

Local denial of service through kernel crash if a privileged user triggers the condition.

🟢

If Mitigated

Minor system instability with automatic recovery if kernel panic handling is configured.

🌐 Internet-Facing: LOW - Requires local access to exploit, not remotely triggerable.

🏢 Internal Only: MEDIUM - Local users or processes could cause system crashes affecting availability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access and ability to trigger device memory allocation failure conditions. Not trivial to exploit reliably.

🛠️ Fix & Mitigation

✅ Official Fix

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

Vendor Advisory: https://git.kernel.org/stable/c/3046b011d368162b1b9ca9453eee0fea930e0a93

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version. 2. Reboot system to load new kernel. 3. Verify mlx5 driver is loaded from patched kernel.

🔧 Temporary Workarounds

Disable mlx5 driver

Linux

Prevent loading of vulnerable mlx5 network driver if Mellanox hardware is not required

echo 'blacklist mlx5_core' > /etc/modprobe.d/blacklist-mlx5.conf
update-initramfs -u
reboot

🧯 If You Can't Patch

Restrict local user access to prevent potential exploitation
Implement kernel crash monitoring and automatic recovery mechanisms

🔍 How to Verify

Check if Vulnerable:

Check kernel version and verify if mlx5 driver is loaded: lsmod | grep mlx5 && uname -r

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version is updated and check git commit history for the fix: uname -r && zgrep -i '3046b011d368162b1b9ca9453eee0fea930e0a93' /boot/config*

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages in /var/log/kern.log or dmesg
NULL pointer dereference errors mentioning mlx5

Network Indicators:

Sudden loss of network connectivity on Mellanox interfaces

SIEM Query:

source="kernel" AND ("NULL pointer dereference" OR "kernel panic") AND "mlx5"

📊 Metadata

CVE ID: CVE-2025-38645

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: 0.02% exploit probability (2.6th percentile)

Published: August 22, 2025

Last Updated: January 7, 2026

🔗 References

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🔗 Related Vulnerabilities

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