CVE-2023-4208
📋 TL;DR
This CVE describes a use-after-free vulnerability in the Linux kernel's net/sched: cls_u32 traffic control subsystem. It allows a local attacker to escalate privileges from an unprivileged user to root. All Linux systems using affected kernel versions are vulnerable.
💻 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 →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
Full root privilege escalation leading to complete system compromise, data theft, and persistent backdoor installation.
Likely Case
Local privilege escalation allowing attackers to bypass security controls, install malware, or access sensitive data.
If Mitigated
Limited impact if proper access controls restrict local user accounts and containerization/isolation is implemented.
🎯 Exploit Status
Requires local access and knowledge of kernel exploitation techniques. No public exploit code is known at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel with commit 3044b16e7c6fe5d24b1cdbcf1bd0a9d92d1ebd81
Vendor Advisory: https://www.debian.org/security/2023/dsa-5492
Restart Required: Yes
Instructions:
1. Update kernel package using distribution's package manager. 2. For Debian/Ubuntu: apt update && apt upgrade linux-image-*. 3. For RHEL/CentOS: yum update kernel. 4. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable cls_u32 module
linuxPrevent loading of vulnerable kernel module
echo 'install cls_u32 /bin/false' >> /etc/modprobe.d/disable-cls_u32.conf
rmmod cls_u32
🧯 If You Can't Patch
- Restrict local user access and implement strict privilege separation
- Use containerization with proper security profiles to limit kernel access
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if commit 3044b16e7c6fe5d24b1cdbcf1bd0a9d92d1ebd81 is presentCheck Version:
uname -rVerify Fix Applied:
Verify kernel version after update and check that cls_u32 module is either patched or disabled📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- OOM killer activity related to kernel memory
- Unusual privilege escalation attempts
Network Indicators:
- None - this is a local vulnerability
SIEM Query:
source="kernel" AND ("panic" OR "Oops" OR "general protection fault")🔗 References
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3044b16e7c6fe5d24b1cdbcf1bd0a9d92d1ebd81
- https://kernel.dance/3044b16e7c6fe5d24b1cdbcf1bd0a9d92d1ebd81
- https://lists.debian.org/debian-lts-announce/2024/01/msg00004.html
- https://www.debian.org/security/2023/dsa-5492
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3044b16e7c6fe5d24b1cdbcf1bd0a9d92d1ebd81
- https://kernel.dance/3044b16e7c6fe5d24b1cdbcf1bd0a9d92d1ebd81
- https://lists.debian.org/debian-lts-announce/2024/01/msg00004.html
- https://www.debian.org/security/2023/dsa-5492
