CVE-2025-39853 – This CVE describes a memory access vulnerabilit... (How to Fix)

Q: What is the severity of CVE-2025-39853?

CVE-2025-39853 has a CVSS score of 7.1 (HIGH). This CVE describes a memory access vulnerability in the Linux kernel's i40e network driver. When the MAC address list is empty, the driver uses list_first_entry() which can return a pointer to invalid memory, potentially leading to kernel crashes or other undefined behavior. This affects systems using Intel Ethernet 700 Series network adapters with vulnerable kernel versions.

📋 TL;DR

This CVE describes a memory access vulnerability in the Linux kernel's i40e network driver. When the MAC address list is empty, the driver uses list_first_entry() which can return a pointer to invalid memory, potentially leading to kernel crashes or other undefined behavior. This affects systems using Intel Ethernet 700 Series network adapters with vulnerable kernel versions.

💻 Affected Systems

Products:

Linux kernel with i40e driver

Versions: Kernel versions containing the vulnerable i40e driver code before the fix commits

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires Intel Ethernet 700 Series network adapter and i40e driver usage. The vulnerability triggers when MAC address list becomes empty during network operations.

📦 What is this software?

Debian Linux by Debian

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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...

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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...

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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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic leading to system crash, denial of service, or potential privilege escalation if memory corruption can be controlled.

🟠

Likely Case

System crash or kernel panic when network operations trigger the empty MAC list condition, causing denial of service.

🟢

If Mitigated

System remains stable with no impact if the vulnerable code path isn't triggered or if patched.

🌐 Internet-Facing: MEDIUM - Network-facing systems could be crashed remotely if attackers can trigger the empty MAC list condition.

🏢 Internal Only: MEDIUM - Internal systems could experience crashes affecting availability, but requires specific network conditions.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation requires triggering the specific code path where MAC list is empty, which may require network manipulation or specific network conditions.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing the fix commits: 1eadabcf5623f1237a539b16586b4ed8ac8dffcd, 3c6fb929afa313d9d11f780451d113f73922fe5d, 66e7cdbda74ee823ec2bf7b830ebd235c54f5ddf, 971feafe157afac443027acdc235badc6838560b, 9c21fc4cebd44dd21016c61261a683af390343f8

Vendor Advisory: https://git.kernel.org/stable/c/1eadabcf5623f1237a539b16586b4ed8ac8dffcd

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. Rebuild kernel if compiling from source. 3. Reboot system to load patched kernel.

🔧 Temporary Workarounds

Disable i40e driver

linux

Remove or blacklist the i40e driver to prevent loading

echo 'blacklist i40e' >> /etc/modprobe.d/blacklist-i40e.conf
update-initramfs -u
reboot

Use alternative network driver

linux

Switch to ixgbe driver if compatible with hardware

modprobe -r i40e
modprobe ixgbe

🧯 If You Can't Patch

Monitor system logs for kernel panics or crashes related to i40e driver
Implement network segmentation to limit exposure to potential triggers

🔍 How to Verify

Check if Vulnerable:

Check kernel version and if i40e module is loaded: lsmod | grep i40e && uname -r

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes fix commits and i40e driver loads without errors in dmesg

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages
i40e driver errors in dmesg
System crash logs

Network Indicators:

Sudden network interface disappearance
Unexpected network service interruptions

SIEM Query:

source="kernel" AND ("panic" OR "Oops" OR "i40e")

📊 Metadata

CVE ID: CVE-2025-39853

CVSS v3 Score: 7.1 (HIGH)

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

CWE: CWE-125

EPSS Score: 0.02% exploit probability (5.3th percentile)

Published: September 19, 2025

Last Updated: January 20, 2026

🔗 References

https://git.kernel.org/stable/c/1eadabcf5623f1237a539b16586b4ed8ac8dffcd Patch
https://git.kernel.org/stable/c/3c6fb929afa313d9d11f780451d113f73922fe5d Patch
https://git.kernel.org/stable/c/66e7cdbda74ee823ec2bf7b830ebd235c54f5ddf Patch
https://git.kernel.org/stable/c/971feafe157afac443027acdc235badc6838560b Patch
https://git.kernel.org/stable/c/9c21fc4cebd44dd21016c61261a683af390343f8 Patch
https://git.kernel.org/stable/c/a556f06338e1d5a85af0e32ecb46e365547f92b9 Patch
https://git.kernel.org/stable/c/e2a5e74879f9b494bbd66fa93f355feacde450c7 Patch
https://git.kernel.org/stable/c/fb216d980fae6561c7c70af8ef826faf059c6515 Patch
https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html Third Party Advisory,Mailing List
https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html Third Party Advisory,Mailing List

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