CVE-2023-4206
📋 TL;DR
This CVE describes a use-after-free vulnerability in the Linux kernel's net/sched: cls_route component that allows local attackers to escalate privileges. Attackers can exploit this flaw to gain root access on affected systems. All Linux systems using vulnerable kernel versions are potentially affected.
💻 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 system compromise with root privileges, allowing complete control over the system, data theft, and persistence establishment.
Likely Case
Local privilege escalation from unprivileged user to root, enabling installation of malware, data access, and further lateral movement.
If Mitigated
Limited impact if proper access controls restrict local user accounts and containerization/sandboxing is implemented.
🎯 Exploit Status
Exploitation requires local access and knowledge of kernel exploitation techniques. The use-after-free condition must be carefully triggered to achieve reliable privilege escalation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel with commit b80b829e9e2c1b3f7aae34855e04d8f6ecaf13c8
Vendor Advisory: https://www.debian.org/security/2023/dsa-5492
Restart Required: Yes
Instructions:
1. Update kernel packages using your distribution's package manager. 2. For Debian/Ubuntu: sudo apt update && sudo apt upgrade linux-image-*. 3. For RHEL/CentOS: sudo yum update kernel. 4. Reboot the system to load the new kernel.
🔧 Temporary Workarounds
Disable CONFIG_NET_CLS_ROUTE4
linuxRemove the vulnerable kernel module by disabling the route4 classifier in traffic control
sudo modprobe -r cls_route4
echo 'blacklist cls_route4' | sudo tee /etc/modprobe.d/blacklist-cls_route4.conf
Restrict user access
linuxLimit local user accounts and implement strict access controls to reduce attack surface
sudo useradd -r -s /sbin/nologin restricted_user
sudo passwd -l username_to_lock
🧯 If You Can't Patch
- Implement strict access controls to limit local user accounts and shell access
- Use containerization or virtualization to isolate workloads and limit kernel exposure
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if commit b80b829e9e2c1b3f7aae34855e04d8f6ecaf13c8 is present: uname -r && git log --oneline | grep b80b829e9e2c1b3f7aae34855e04d8f6ecaf13c8Check Version:
uname -rVerify Fix Applied:
Verify kernel version is updated and the commit is present: uname -r && grep -q b80b829e9e2c1b3f7aae34855e04d8f6ecaf13c8 /proc/version📡 Detection & Monitoring
Log Indicators:
- Kernel oops messages or crashes in /var/log/kern.log
- Unusual privilege escalation attempts in auth logs
- Abnormal traffic control operations
Network Indicators:
- Local exploitation only - no network indicators
SIEM Query:
source="kern.log" AND ("Oops" OR "general protection fault" OR "use-after-free") OR source="auth.log" AND "sudo" AND "FAILED"🔗 References
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b80b829e9e2c1b3f7aae34855e04d8f6ecaf13c8
- https://kernel.dance/b80b829e9e2c1b3f7aae34855e04d8f6ecaf13c8
- 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=b80b829e9e2c1b3f7aae34855e04d8f6ecaf13c8
- https://kernel.dance/b80b829e9e2c1b3f7aae34855e04d8f6ecaf13c8
- https://lists.debian.org/debian-lts-announce/2024/01/msg00004.html
- https://www.debian.org/security/2023/dsa-5492
