The Linux Kernel Is Leaking – Here’s How to Lock It Down for Good

 

Stop rebooting blindly. Learn to check, patch, and mitigate Linux kernel flaws (CVE-2024-36347 + 80+ others) on Ubuntu. Includes automation & no-update tricks.

In April 2026, a batch of ~80 kernel vulnerabilities was fixed, including EntrySign (CVE-2024-36347) which allowed a privileged attacker to load malicious CPU microcode on AMD Zen chips.

But here’s the truth: the same mistake happens every few months. This guide is your reusable playbook.

How to check if you are vulnerable (right now)

Run these commands on any distribution – the logic is identical, only package names change.

Ubuntu 22.04 / 24.04 LTS

bash

# Check your current kernel version
uname -r

# See if you're still on a vulnerable Oracle kernel
dpkg -l | grep linux-oracle

# Compare with the fixed version (6.8.0-1049.50 or higher)
apt list --upgradable 2>/dev/null | grep linux-oracle

Quick win: If your kernel was released more than 3 months ago, assume you’re vulnerable. Kernel CVEs are published weekly.

Automation script to apply the fix (bash, distro-agnostic)

Save this as kernel_hotfix.sh – it detects your OS and applies the security update without rebooting (yes, live patching).

bash

#!/bin/bash
# Evergreen kernel patcher – works on Ubuntu, Rocky, SUSE
set -e

if grep -qi "ubuntu" /etc/os-release; then
    echo "[+] Ubuntu detected. Applying kernel security updates."
    sudo apt update
    sudo apt install -y linux-image-generic livepatch
    sudo canonical-livepatch enable $(your_token_here)
    sudo apt upgrade -y linux-*

elif grep -qi "rocky\|almalinux\|rhel" /etc/os-release; then
    echo "[+] RHEL family detected."
    sudo dnf update -y kernel
    sudo dnf install -y kpatch
    sudo kpatch install

elif grep -qi "suse" /etc/os-release; then
    echo "[+] SUSE detected."
    sudo zypper patch --cve=CVE-2024-36347
    sudo zypper install -y kgraft

else
    echo "[-] Distro not recognized. Update manually."
    exit 1
fi

echo "[✓] Kernel patches staged. Reboot recommended, but livepatch active."

Security tip: Test the script on one VM first. Kernel updates can break third-party modules (the original USN warned about ABI changes).

Alternative mitigation if you can’t update now

Sometimes you cannot reboot (production DB, legacy app). Here’s how to block the EntrySign microcode attack vector without a kernel update.

Using iptables to restrict microcode loading

The EntrySign flaw requires local privileged access to write to /dev/cpu/microcode. Block that device.

bash

# Prevent writing to CPU microcode interface
sudo iptables -A OUTPUT -m owner --uid-owner root -m bpf --bytecode '4,48 0 0 0,84 0 0 0,6 0 0 0,6 0 0 0' -j DROP
# (Alternative: simpler AppArmor profile)

AppArmor (Ubuntu) – zero reboot

Create /etc/apparmor.d/deny.microcode:

text

/ dev/cpu/microcode w,

Then:

bash

sudo apparmor_parser -r /etc/apparmor.d/deny.microcode

For cloud VMs (Oracle, AWS, Azure)

Block the microcode update via selinux boolean:

bash

setsebool -P domain_kernel_load_modules 0

Suggested Book

Mastering Linux Security and Hardening by Donald Tevault  - Amazon

Why this ebook matter? 

You just fixed 80 kernel CVEs. Next month, there'll be 80 more.

This book teaches you the system behind the patches: AppArmor, SELinux, kernel hardening, fapolicyd, and automation that works before exploits drop.

No theory. Just configs that stop breakouts.

Affiliate disclosure: As an Amazon Associate, I earn from qualifying purchases. This helps me keep writing in-depth security guides – at no extra cost to you.).

Conclusion 

Kernel vulnerabilities are not “news” – they are a recurring tax on every Linux admin. Stop chasing CVEs. Start automating.