CVE-2024-49966 – This CVE describes a use-after-free vulnerabili... (How to Fix)

Q: What is the severity of CVE-2024-49966?

CVE-2024-49966 has a CVSS score of 7.8 (HIGH). This CVE describes a use-after-free vulnerability in the Linux kernel's OCFS2 filesystem quota handling. When an error occurs during global quota reading, the system fails to properly cancel a scheduled work item before freeing memory, potentially leading to kernel memory corruption. This affects Linux systems using the OCFS2 filesystem with quota support enabled.

📋 TL;DR

This CVE describes a use-after-free vulnerability in the Linux kernel's OCFS2 filesystem quota handling. When an error occurs during global quota reading, the system fails to properly cancel a scheduled work item before freeing memory, potentially leading to kernel memory corruption. This affects Linux systems using the OCFS2 filesystem with quota support enabled.

💻 Affected Systems

Products:

Linux Kernel

Versions: Specific affected kernel versions not explicitly stated in CVE, but patches exist in stable kernel trees.

Operating Systems: Linux distributions using affected kernel versions with OCFS2 support

Default Config Vulnerable: ✅ No

Notes: Only vulnerable when OCFS2 filesystem is in use with quota support enabled. Most Linux distributions don't enable 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

Kernel panic leading to system crash and denial of service, or potential privilege escalation if an attacker can trigger the condition and control memory corruption.

🟠

Likely Case

System crash or kernel panic causing denial of service when the specific error condition is triggered during quota operations.

🟢

If Mitigated

No impact if OCFS2 filesystem is not used or quota support is disabled.

🌐 Internet-Facing: LOW - Requires local access or ability to trigger specific filesystem operations.

🏢 Internal Only: MEDIUM - Local users or processes with appropriate permissions could potentially trigger the vulnerability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: HIGH

Exploitation requires triggering specific error conditions in OCFS2 quota handling, which may require local access and specific permissions.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Patches available in stable kernel trees (commits referenced in CVE)

Vendor Advisory: https://git.kernel.org/stable/c/0d707a33c84b371cb66120e198eed3374726ddd8

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version from your distribution's repositories. 2. Reboot system to load new kernel.

🔧 Temporary Workarounds

Disable OCFS2 quota support

linux

Prevent use of OCFS2 filesystem quota functionality

# Remove quota mount options from OCFS2 filesystems in /etc/fstab
# Ensure no OCFS2 filesystems are mounted with usrquota,grpquota options

Avoid OCFS2 usage

linux

Use alternative filesystems instead of OCFS2

# Migrate data from OCFS2 to alternative filesystem like ext4, xfs

🧯 If You Can't Patch

Disable OCFS2 filesystem usage entirely
Implement strict access controls to prevent unauthorized users from triggering quota operations

🔍 How to Verify

Check if Vulnerable:

Check if OCFS2 filesystems are mounted: mount | grep ocfs2. Check kernel version against patched versions from your distribution.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version after update matches patched version. Check that OCFS2 modules load without errors.

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages
ODEBUG warnings about timer_list objects
OCFS2 quota-related errors in dmesg

Network Indicators:

None - local vulnerability

SIEM Query:

source="kernel" AND ("ODEBUG" OR "timer_list" OR "qsync_work_fn" OR "ocfs2" AND "panic")

📊 Metadata

CVE ID: CVE-2024-49966

CVSS v3 Score: 7.8 (HIGH)

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

CWE: CWE-416

Published: October 21, 2024

Last Updated: November 3, 2025

🔗 References

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