CVE-2023-53619
📋 TL;DR
This CVE describes a use-after-free vulnerability in the Linux kernel's netfilter conntrack subsystem. When nf_conntrack initialization fails, the nf_ct_helper_hash map is freed, but subsequent module loading can still access this dangling pointer, potentially causing memory corruption. This affects Linux systems with CONFIG_NF_CONNTRACK=y and netfilter modules like netfilter_conntrack_ftp.
💻 Affected Systems
- Linux kernel
⚠️ Risk & Real-World Impact
Worst Case
Kernel panic, system crash, or arbitrary code execution with kernel privileges leading to complete system compromise.
Likely Case
System instability, crashes, or denial of service due to memory corruption when loading conntrack modules after initialization failure.
If Mitigated
No impact if the system doesn't use affected netfilter modules or if initialization doesn't fail.
🎯 Exploit Status
Exploitation requires specific conditions: nf_conntrack initialization failure followed by loading of affected netfilter modules.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in kernel commits: 00716f25f9697d02a0d9bd622575c7c7321ba3d0, 05561f822f27b9fa88fa5504ddec34bf38833034, 4ee69c91cb8f9ca144bc0861969e5a1a3c6152a7, 61c7a5256543ae7d24cd9d21853d514c8632e1e9, 6eef7a2b933885a17679eb8ed0796ddf0ee5309b
Vendor Advisory: https://git.kernel.org/stable/c/00716f25f9697d02a0d9bd622575c7c7321ba3d0
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix commits. 2. Check distribution-specific security advisories. 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable vulnerable modules
linuxPrevent loading of netfilter conntrack helper modules that could trigger the vulnerability
modprobe -r nf_conntrack_ftp
echo 'blacklist nf_conntrack_ftp' >> /etc/modprobe.d/blacklist.conf
Ensure proper initialization
linuxMonitor and ensure nf_conntrack initialization doesn't fail during boot
dmesg | grep -i 'nf_conntrack'
systemctl status systemd-modules-load
🧯 If You Can't Patch
- Avoid loading netfilter conntrack helper modules like nf_conntrack_ftp
- Implement strict module loading policies and monitor for nf_conntrack initialization failures
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if it contains the fix commits: uname -r and examine kernel source or distribution security advisoriesCheck Version:
uname -rVerify Fix Applied:
Verify kernel version is updated and check that the fix commits are present in kernel source📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages
- Oops messages related to nf_conntrack
- Failed module loading messages
Network Indicators:
- Unexpected system crashes when network modules are loaded
SIEM Query:
source="kernel" AND ("nf_conntrack" OR "use-after-free" OR "kernel panic")🔗 References
- https://git.kernel.org/stable/c/00716f25f9697d02a0d9bd622575c7c7321ba3d0
- https://git.kernel.org/stable/c/05561f822f27b9fa88fa5504ddec34bf38833034
- https://git.kernel.org/stable/c/4ee69c91cb8f9ca144bc0861969e5a1a3c6152a7
- https://git.kernel.org/stable/c/61c7a5256543ae7d24cd9d21853d514c8632e1e9
- https://git.kernel.org/stable/c/6eef7a2b933885a17679eb8ed0796ddf0ee5309b
- https://git.kernel.org/stable/c/6f03ce2f1abcb9f9d0511e3659ca6eb60e39f566
- https://git.kernel.org/stable/c/8289d422f5e484efe4a565fe18e862ecd621c175
- https://git.kernel.org/stable/c/fce5cc7cbd4b92f979bf02c9ec5fb69aaeba92d7
