CVE-2026-23183 – A NULL pointer dereference vulnerability in the... (How to Fix)

Q: What is the severity of CVE-2026-23183?

CVE-2026-23183 has a CVSS score of N/A (Unknown). A NULL pointer dereference vulnerability in the Linux kernel's cgroup/dmem subsystem allows local attackers to trigger a kernel panic (denial of service) by writing invalid data to the dmem.max control file. This affects systems using the dmem cgroup controller with Linux kernel versions containing the vulnerable code. Only local users with write access to cgroup control files can exploit this.

📋 TL;DR

A NULL pointer dereference vulnerability in the Linux kernel's cgroup/dmem subsystem allows local attackers to trigger a kernel panic (denial of service) by writing invalid data to the dmem.max control file. This affects systems using the dmem cgroup controller with Linux kernel versions containing the vulnerable code. Only local users with write access to cgroup control files can exploit this.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific versions containing vulnerable dmem cgroup code (exact range not specified in CVE, but appears in 6.19.0-rc6-next-2026012 and earlier)

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires dmem cgroup controller to be enabled and accessible. Attack requires write permissions to /sys/fs/cgroup/dmem.max or similar control files.

⚠️ 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.

Recommended Actions:

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 and denial of service, potentially causing data loss or service disruption.

🟠

Likely Case

Local denial of service through kernel panic, requiring system reboot to recover.

🟢

If Mitigated

No impact if proper access controls prevent unauthorized users from writing to cgroup control files.

🌐 Internet-Facing: LOW - Requires local access to the system; not directly exploitable over network.

🏢 Internal Only: MEDIUM - Local users or compromised accounts with cgroup write permissions can cause system crashes.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires local access and knowledge of cgroup interface. The vulnerability was discovered through normal testing/development.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Patched in kernel commits 43151f812886be1855d2cba059f9c93e4729460b and c13816e8fa23deec6a8d7465d9e637fd02683b5c

Vendor Advisory: https://git.kernel.org/stable/c/43151f812886be1855d2cba059f9c93e4729460b

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing fixes. 2. Check with distribution vendor for backported patches. 3. Reboot system after kernel update.

🔧 Temporary Workarounds

Restrict cgroup access

all

Limit write access to dmem cgroup control files to prevent unauthorized users from triggering the vulnerability.

chmod 644 /sys/fs/cgroup/dmem.max
chown root:root /sys/fs/cgroup/dmem.max

Disable dmem cgroup controller

all

Remove dmem from cgroup controllers if not required for system functionality.

echo "-dmem" > /sys/fs/cgroup/cgroup.subtree_control

🧯 If You Can't Patch

Implement strict access controls on cgroup filesystems
Monitor for unauthorized cgroup write attempts and system crashes

🔍 How to Verify

Check if Vulnerable:

Check kernel version and if dmem cgroup controller is active: cat /proc/cgroups | grep dmem

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version is newer than vulnerable version and test writing to dmem.max with invalid input no longer causes crash

📡 Detection & Monitoring

Log Indicators:

Kernel panic logs with NULL pointer dereference in dmemcg_limit_write
System crash/reboot events following cgroup write operations

Network Indicators:

None - local vulnerability only

SIEM Query:

Search for kernel logs containing 'dmemcg_limit_write' or 'NULL pointer dereference' in cgroup context

📊 Metadata

CVE ID: CVE-2026-23183

CVSS v3 Score: N/A (Unknown)

Published: February 14, 2026

Last Updated: February 18, 2026

🔗 References

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