CVE-2026-23204
📋 TL;DR
A memory corruption vulnerability in the Linux kernel's traffic classifier subsystem allows attackers to trigger out-of-bounds memory access via specially crafted network packets. This affects Linux systems with the u32 classifier enabled in the kernel's network scheduling layer. The vulnerability could lead to kernel crashes or potential privilege escalation.
💻 Affected Systems
- Linux kernel
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to system crash, or potential privilege escalation to kernel mode allowing complete system compromise.
Likely Case
Denial of service through kernel crash or system instability when processing malicious network traffic.
If Mitigated
Limited impact if proper network segmentation and traffic filtering are implemented to block malicious packets.
🎯 Exploit Status
Exploitation requires sending specially crafted network packets to a system with u32 classifier enabled; no public exploit code available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions with commits 13336a6239b9d7c6e61483017bb8bdfe3ceb10a5, 8a672f177ebe19c93d795fbe967846084fbc7943, cabd1a976375780dabab888784e356f574bbaed8, or e41a23e61259f5526af875c3b86b3d42a9bae0e5
Vendor Advisory: https://git.kernel.org/stable/c/13336a6239b9d7c6e61483017bb8bdfe3ceb10a5
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 u32 classifier
allRemove or disable u32 traffic classifier rules if not required
tc filter del dev <interface> parent <handle>
Remove u32 rules from /etc/network configuration
Network traffic filtering
allImplement network filtering to block malicious packets targeting this vulnerability
iptables -A INPUT -m u32 --u32 "0>>22&0x3C@ 12>>26&0x3C@ 0=0x800" -j DROP
Configure firewall rules to restrict traffic to trusted sources
🧯 If You Can't Patch
- Disable u32 traffic classifier functionality entirely
- Implement strict network segmentation and firewall rules to limit exposure
🔍 How to Verify
Check if Vulnerable:
Check if u32 classifier is configured: tc filter show | grep -i u32Check Version:
uname -rVerify Fix Applied:
Check kernel version contains fix commits: uname -r and verify with distribution patch notes📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages
- KASAN error reports in dmesg
- System crash/reboot logs
Network Indicators:
- Unusual network traffic patterns targeting traffic classification
- Spike in malformed packet attempts
SIEM Query:
source="kernel" AND ("KASAN" OR "slab-out-of-bounds" OR "u32_classify")