CVE-2025-39911

Q: What is the severity of CVE-2025-39911?

CVE-2025-39911 has a CVSS score of 7.8 (HIGH). A Linux kernel vulnerability in the i40e network driver causes incorrect IRQ cleanup during error handling, leading to kernel warnings and potential system instability. This affects systems using Intel Ethernet 700 Series network adapters with the i40e driver. The issue occurs when network interface setup fails, triggering improper interrupt request deallocation.

7.8 HIGH

📋 TL;DR

A Linux kernel vulnerability in the i40e network driver causes incorrect IRQ cleanup during error handling, leading to kernel warnings and potential system instability. This affects systems using Intel Ethernet 700 Series network adapters with the i40e driver. The issue occurs when network interface setup fails, triggering improper interrupt request deallocation.

💻 Affected Systems

Products:

Linux kernel with i40e driver

Versions: Kernel versions containing vulnerable i40e driver code (specific versions not specified in CVE)

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires Intel Ethernet 700 Series network adapter with i40e driver loaded and network interface configuration operations.

📦 What is this software?

Debian Linux by Debian

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Linux Kernel by Linux

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⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic or system crash due to resource exhaustion from unfreed IRQs, causing denial of service and potential data loss.

🟠

Likely Case

Kernel warning messages in system logs and temporary network interface failures during setup, requiring system restart to recover.

🟢

If Mitigated

Minor performance impact with warning messages but no service disruption if error doesn't occur during normal operation.

🌐 Internet-Facing: LOW - Requires local access to trigger the vulnerable code path through network interface configuration.

🏢 Internal Only: MEDIUM - Internal administrators or automated tools modifying network configurations could trigger the issue.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires ability to trigger network interface configuration failures, typically requiring local system access or administrative privileges.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Patched in kernel commits referenced in CVE (e.g., 13ab9adef3cd386511c930a9660ae06595007f89)

Vendor Advisory: https://git.kernel.org/stable/c/13ab9adef3cd386511c930a9660ae06595007f89

Restart Required: Yes

Instructions:

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

🔧 Temporary Workarounds

Avoid network interface reconfiguration

linux

Prevent triggering the vulnerable error path by avoiding network interface setup operations that could fail.

Unload i40e driver

linux

Remove the vulnerable driver if Intel Ethernet 700 Series adapter is not required.

sudo rmmod i40e

🧯 If You Can't Patch

Monitor system logs for 'Trying to free already-free IRQ' warnings and restart affected systems if detected
Implement strict change control for network configuration to minimize interface setup operations

🔍 How to Verify

Check if Vulnerable:

Check kernel version and i40e driver presence: 'uname -r' and 'lsmod | grep i40e'

Check Version:

uname -r

Verify Fix Applied:

Verify kernel includes fix commits: 'git log --oneline | grep -i "i40e.*irq.*free"' or check kernel changelog

📡 Detection & Monitoring

Log Indicators:

kernel: Trying to free already-free IRQ
kernel: WARNING: CPU: ... at kernel/irq/manage.c

Network Indicators:

Network interface configuration failures
Unexpected network adapter restarts

SIEM Query:

source="kernel" AND "Trying to free already-free IRQ"

📊 Metadata

CVE ID: CVE-2025-39911

CVSS v3 Score: 7.8 (HIGH)

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

EPSS Score: 0.03% exploit probability (6.9th percentile)

Published: October 1, 2025

Last Updated: January 16, 2026

📋 TL;DR

💻 Affected Systems

📦 What is this software?

Debian Linux by Debian

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

⚠️ Risk & Real-World Impact

Worst Case

Likely Case

If Mitigated

🎯 Exploit Status

🛠️ Fix & Mitigation

✅ Official Fix

Instructions:

🔧 Temporary Workarounds

Avoid network interface reconfiguration

Unload i40e driver

🧯 If You Can't Patch

🔍 How to Verify

Check if Vulnerable:

Check Version:

Verify Fix Applied:

📡 Detection & Monitoring

Log Indicators:

Network Indicators:

SIEM Query:

📊 Metadata

🔗 References

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