CVE-2023-52927
📋 TL;DR
This Linux kernel vulnerability in the netfilter subsystem allows expectations (exp) to remain in hash tables when they should be removed, potentially leading to use-after-free conditions. It affects Linux systems using netfilter conntrack functionality, particularly those with OVS or TC conntrack configurations. Attackers could exploit this to cause kernel crashes or potentially execute arbitrary code.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to system crash or potential arbitrary code execution with kernel privileges, resulting in complete system compromise.
Likely Case
System instability, kernel crashes, or denial of service affecting network connectivity and system reliability.
If Mitigated
Minimal impact if systems are patched or don't use affected netfilter configurations; isolated crashes in specific network scenarios.
🎯 Exploit Status
Exploitation requires understanding of netfilter internals and specific system configurations. No public exploit code identified in references.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing fixes from commits 3fa58a6fbd1e9e5682d09cdafb08fba004cb12ec and 4914109a8e1e494c6aa9852f9e84ec77a5fc643f
Vendor Advisory: https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution vendor. 2. Reboot system to load new kernel. 3. Verify kernel version after reboot.
🔧 Temporary Workarounds
Disable affected netfilter modules
LinuxIf OVS or TC conntrack functionality is not required, disable these modules to prevent exploitation.
modprobe -r openvswitch
modprobe -r act_ct
echo 'blacklist openvswitch' >> /etc/modprobe.d/blacklist.conf
echo 'blacklist act_ct' >> /etc/modprobe.d/blacklist.conf
🧯 If You Can't Patch
- Implement network segmentation to limit access to systems using OVS/TC conntrack
- Monitor system logs for kernel panic or crash indicators and implement rapid response procedures
🔍 How to Verify
Check if Vulnerable:
Check if system uses OVS or TC conntrack and has unpatched kernel. Examine kernel configuration and loaded modules.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits and test OVS/TC conntrack functionality remains stable.📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages
- Netfilter/conntrack error logs
- System crash dumps
Network Indicators:
- Unexpected connection tracking behavior
- Network service disruptions
SIEM Query:
source="kernel" AND ("panic" OR "Oops" OR "BUG") AND ("netfilter" OR "conntrack" OR "OVS")