CVE-2023-3609
📋 TL;DR
This CVE describes a use-after-free vulnerability in the Linux kernel's net/sched: cls_u32 component that allows local privilege escalation. Attackers with local access can exploit improper reference counting to gain root privileges. 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
Local attacker gains full root privileges, compromising the entire system and potentially pivoting to other systems in the network.
Likely Case
Local user or compromised service escalates to root, enabling persistence, data theft, and further network exploitation.
If Mitigated
With proper access controls and minimal local user accounts, impact is limited to specific compromised services.
🎯 Exploit Status
Exploit requires local access and knowledge of kernel exploitation techniques. Public exploit code exists in security advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel with commit 04c55383fa5689357bcdd2c8036725a55ed632bc or later
Vendor Advisory: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=04c55383fa5689357bcdd2c8036725a55ed632bc
Restart Required: Yes
Instructions:
1. Update kernel package using distribution's package manager. 2. For Debian: 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
linuxUnload the vulnerable kernel module if not required
rmmod cls_u32
echo 'blacklist cls_u32' >> /etc/modprobe.d/blacklist.conf
🧯 If You Can't Patch
- Restrict local user access and implement strict privilege separation
- Monitor for privilege escalation attempts and kernel module loading
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if commit 04c55383fa5689357bcdd2c8036725a55ed632bc is present: uname -r && git log --oneline | grep 04c55383fa5689357bcdd2c8036725a55ed632bcCheck Version:
uname -rVerify Fix Applied:
Verify kernel version is updated and commit appears in kernel changelog📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- Failed privilege escalation attempts in audit logs
- Unexpected kernel module operations
Network Indicators:
- None - local exploit only
SIEM Query:
source="kernel" AND ("panic" OR "oops") OR source="audit" AND "privilege" AND "escalation"🔗 References
- http://packetstormsecurity.com/files/175072/Kernel-Live-Patch-Security-Notice-LSN-0098-1.html
- http://packetstormsecurity.com/files/175963/Kernel-Live-Patch-Security-Notice-LSN-0099-1.html
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=04c55383fa5689357bcdd2c8036725a55ed632bc
- https://kernel.dance/04c55383fa5689357bcdd2c8036725a55ed632bc
- https://lists.debian.org/debian-lts-announce/2023/10/msg00027.html
- https://lists.debian.org/debian-lts-announce/2024/01/msg00004.html
- https://security.netapp.com/advisory/ntap-20230818-0005/
- https://www.debian.org/security/2023/dsa-5480
- http://packetstormsecurity.com/files/175072/Kernel-Live-Patch-Security-Notice-LSN-0098-1.html
- http://packetstormsecurity.com/files/175963/Kernel-Live-Patch-Security-Notice-LSN-0099-1.html
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=04c55383fa5689357bcdd2c8036725a55ed632bc
- https://kernel.dance/04c55383fa5689357bcdd2c8036725a55ed632bc
- https://lists.debian.org/debian-lts-announce/2023/10/msg00027.html
- https://lists.debian.org/debian-lts-announce/2024/01/msg00004.html
- https://security.netapp.com/advisory/ntap-20230818-0005/
- https://www.debian.org/security/2023/dsa-5480
