CVE-2024-40958 – This is a use-after-free vulnerability in the L... (How to Fix)

Q: What is the severity of CVE-2024-40958?

CVE-2024-40958 has a CVSS score of 7.8 (HIGH). This is a use-after-free vulnerability in the Linux kernel's network namespace handling. It allows local attackers to trigger a kernel panic (denial of service) by manipulating network device references. Any system running an affected Linux kernel version is vulnerable.

📋 TL;DR

This is a use-after-free vulnerability in the Linux kernel's network namespace handling. It allows local attackers to trigger a kernel panic (denial of service) by manipulating network device references. Any system running an affected Linux kernel version is vulnerable.

💻 Affected Systems

Products:

Linux kernel

Versions: Kernel versions before the fix commits (specific versions vary by distribution)

Operating Systems: All Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires CAP_NET_ADMIN capability or root access to trigger via tun device 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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic leading to complete system crash and denial of service, potentially requiring physical access to restore functionality.

🟠

Likely Case

Local denial of service through kernel panic, disrupting all services on the affected system.

🟢

If Mitigated

Limited impact if systems are properly segmented and have minimal local user access.

🌐 Internet-Facing: LOW - Requires local access to exploit, not directly exploitable over network.

🏢 Internal Only: HIGH - Any local user or process can potentially trigger the kernel panic.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: LOW

Exploitation requires local access and appropriate privileges (CAP_NET_ADMIN). The trigger sequence is documented in the CVE description.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Fixed in kernel commits: 1b631bffcb2c09551888f3c723f4365c91fe05ef, 2b82028a1f5ee3a8e04090776b10c534144ae77b, 3a6cd326ead7c8bb1f64486789a01974a9f1ad55, 3af28df0d883e8c89a29ac31bc65f9023485743b, cb7f811f638a14590ff98f53c6dd1fb54627d940

Vendor Advisory: https://git.kernel.org/stable/c/1b631bffcb2c09551888f3c723f4365c91fe05ef

Restart Required: Yes

Instructions:

1. Update to a kernel version containing the fix commits
2. Check your distribution's security advisories for specific patched versions
3. Reboot the system after kernel update

🔧 Temporary Workarounds

Restrict tun device access

linux

Limit which users can create and manipulate tun/tap devices to reduce attack surface

# Remove CAP_NET_ADMIN from non-privileged users
# Use Linux capabilities to restrict tun device creation
# Implement mandatory access control (SELinux/AppArmor) policies

🧯 If You Can't Patch

Restrict local user access to systems - only allow trusted administrators
Implement strict capability management to prevent users from obtaining CAP_NET_ADMIN

🔍 How to Verify

Check if Vulnerable:

Check kernel version and compare with distribution's security advisory. Vulnerable if running kernel before fix commits.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes one of the fix commits: 'uname -r' and check with distribution's patch database

📡 Detection & Monitoring

Log Indicators:

Kernel panic logs with refcount_warn_saturate warnings
System crash/reboot events
TUNGETDEVNETNS ioctl operations in audit logs

Network Indicators:

Sudden loss of network connectivity from system crash

SIEM Query:

event_type:"kernel_panic" OR message:"refcount_warn_saturate" OR message:"get_net_ns"

📊 Metadata

CVE ID: CVE-2024-40958

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

CWE: CWE-416

Published: July 12, 2024

Last Updated: November 3, 2025

🔗 References

📤 Share & Export

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🔗 Related Vulnerabilities

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