CVE-2022-48740
📋 TL;DR
This CVE describes a double-free vulnerability in the SELinux subsystem of the Linux kernel. When error conditions occur in certain SELinux policy loading functions, the cond_list_destroy() function can be called twice on the same memory, leading to a NULL pointer dereference and potential kernel panic. This affects all Linux systems using SELinux with vulnerable kernel versions.
💻 Affected Systems
- Linux kernel
📦 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to system crash and denial of service, potentially allowing attackers to disrupt critical systems or create instability for privilege escalation attempts.
Likely Case
System crash or kernel panic when loading malformed SELinux policies, resulting in denial of service and requiring system reboot.
If Mitigated
No impact if SELinux is disabled or if proper policy validation prevents triggering the error path.
🎯 Exploit Status
Exploitation requires ability to trigger error conditions in SELinux policy loading, typically requiring administrative or SELinux policy modification privileges.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits: 186edf7e368c40d06cf727a1ad14698ea67b74ad, 70caa32e6d81f45f0702070c0e4dfe945e92fbd7, 7ed9cbf7ac0d4ed86b356e1b944304ae9ee450d4, f446089a268c8fc6908488e991d28a9b936293db
Vendor Advisory: https://git.kernel.org/stable/c/186edf7e368c40d06cf727a1ad14698ea67b74ad
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution vendor. 2. For RHEL/CentOS: 'yum update kernel'. 3. For Ubuntu/Debian: 'apt update && apt upgrade linux-image-*'. 4. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable SELinux
linuxTemporarily disable SELinux to prevent exploitation (not recommended for production security)
setenforce 0
echo 0 > /selinux/enforce
Restrict SELinux policy modifications
linuxLimit which users can modify SELinux policies to prevent triggering the vulnerability
chmod 600 /etc/selinux/*
setfacl -m u:root:rwx /etc/selinux/
🧯 If You Can't Patch
- Disable SELinux enforcement mode temporarily
- Restrict access to SELinux policy directories to root only
- Monitor for SELinux policy modification attempts
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if SELinux is enabled: 'uname -r' and 'getenforce'Check Version:
uname -rVerify Fix Applied:
Verify kernel version is patched and test SELinux policy loading functionality📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages in /var/log/messages or dmesg
- SELinux policy loading errors
- System crash/reboot events
Network Indicators:
- None - local vulnerability only
SIEM Query:
source="kernel" AND ("panic" OR "NULL pointer dereference" OR "SELinux error")🔗 References
- https://git.kernel.org/stable/c/186edf7e368c40d06cf727a1ad14698ea67b74ad
- https://git.kernel.org/stable/c/70caa32e6d81f45f0702070c0e4dfe945e92fbd7
- https://git.kernel.org/stable/c/7ed9cbf7ac0d4ed86b356e1b944304ae9ee450d4
- https://git.kernel.org/stable/c/f446089a268c8fc6908488e991d28a9b936293db
- https://git.kernel.org/stable/c/186edf7e368c40d06cf727a1ad14698ea67b74ad
- https://git.kernel.org/stable/c/70caa32e6d81f45f0702070c0e4dfe945e92fbd7
- https://git.kernel.org/stable/c/7ed9cbf7ac0d4ed86b356e1b944304ae9ee450d4
- https://git.kernel.org/stable/c/f446089a268c8fc6908488e991d28a9b936293db
