CVE-2024-40951 – This CVE describes a NULL pointer dereference v... (How to Fix)

Q: What is the severity of CVE-2024-40951?

CVE-2024-40951 has a CVSS score of 5.5 (MEDIUM). This CVE describes a NULL pointer dereference vulnerability in the Linux kernel's OCFS2 filesystem driver. When triggered, it causes a kernel panic that crashes the affected system. This affects Linux systems using the OCFS2 clustered filesystem.

📋 TL;DR

This CVE describes a NULL pointer dereference vulnerability in the Linux kernel's OCFS2 filesystem driver. When triggered, it causes a kernel panic that crashes the affected system. This affects Linux systems using the OCFS2 clustered filesystem.

💻 Affected Systems

Products:

Linux kernel with OCFS2 support

Versions: Kernel versions between specific commits introducing and fixing the regression (exact range depends on distribution backports)

Operating Systems: Linux distributions with vulnerable kernel versions

Default Config Vulnerable: ✅ No

Notes: Only vulnerable when OCFS2 filesystem is actually mounted and in use. Most systems don't use OCFS2 by default.

📦 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...

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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

Complete system crash and denial of service, requiring physical or remote console access to reboot the system.

🟠

Likely Case

System crash and denial of service when specific OCFS2 operations trigger the NULL pointer dereference.

🟢

If Mitigated

No impact if OCFS2 is not mounted or used on the system.

🌐 Internet-Facing: LOW - Requires local access or ability to mount OCFS2 filesystems, not typically exposed to internet.

🏢 Internal Only: MEDIUM - Affects systems using OCFS2 for clustering, could disrupt shared storage in enterprise environments.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires ability to trigger OCFS2 journal operations, typically needs local access or ability to mount OCFS2 filesystems.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Fixed in kernel commits 67bcecd780609f471260a8c83fb0ae15f27734ce and related stable backports

Vendor Advisory: https://git.kernel.org/stable/c/67bcecd780609f471260a8c83fb0ae15f27734ce

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version from your distribution vendor. 2. Reboot system to load new kernel. 3. Verify OCFS2 functionality if used.

🔧 Temporary Workarounds

Disable OCFS2 module

linux

Prevent loading of OCFS2 kernel module if not needed

echo 'install ocfs2 /bin/false' >> /etc/modprobe.d/disable-ocfs2.conf
rmmod ocfs2 2>/dev/null || true

Avoid OCFS2 mounts

linux

Ensure no OCFS2 filesystems are mounted

umount -t ocfs2
Remove OCFS2 entries from /etc/fstab

🧯 If You Can't Patch

Ensure OCFS2 kernel module is not loaded and no OCFS2 filesystems are mounted
Monitor systems for kernel panics and have reboot procedures ready

🔍 How to Verify

Check if Vulnerable:

Check if OCFS2 is in use: 'lsmod | grep ocfs2' and 'mount | grep ocfs2'. If either shows OCFS2 active, check kernel version against patched versions.

Check Version:

uname -r

Verify Fix Applied:

After patching, verify kernel version includes fix commit: 'uname -r' and check distribution changelog. Test OCFS2 operations if used.

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages in /var/log/messages or journalctl
NULL pointer dereference errors mentioning ocfs2_abort_trigger()
System crash/reboot events

Network Indicators:

Unplanned node failures in OCFS2 clusters
Storage access interruptions

SIEM Query:

event_source:kernel AND (message:"NULL pointer dereference" OR message:"ocfs2" OR message:"kernel panic")

📊 Metadata

CVE ID: CVE-2024-40951

CVSS v3 Score: 5.5 (MEDIUM)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CWE: CWE-476

Published: July 12, 2024

Last Updated: April 16, 2025

🔗 References

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🔗 Related Vulnerabilities

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