CVE-2024-56693 – This CVE describes a use-after-free vulnerabili... (How to Fix)

Q: What is the severity of CVE-2024-56693?

CVE-2024-56693 has a CVSS score of 7.8 (HIGH). This CVE describes a use-after-free vulnerability in the Linux kernel's brd (block RAM disk) module that occurs during module initialization failure. Attackers could potentially exploit this to cause kernel crashes or execute arbitrary code with kernel privileges. Systems running vulnerable Linux kernel versions with the brd module loaded are affected.

📋 TL;DR

This CVE describes a use-after-free vulnerability in the Linux kernel's brd (block RAM disk) module that occurs during module initialization failure. Attackers could potentially exploit this to cause kernel crashes or execute arbitrary code with kernel privileges. Systems running vulnerable Linux kernel versions with the brd module loaded are affected.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific vulnerable versions not explicitly stated in CVE description, but references indicate fixes in stable kernel trees. Likely affects versions before the fix commits.

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ✅ No

Notes: Only vulnerable if the brd module is loaded (either manually via modprobe or automatically by system). Many systems don't load this module 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...

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 or potential arbitrary code execution with kernel privileges, resulting in complete system compromise.

🟠

Likely Case

Kernel panic causing system crash and denial of service, requiring system reboot.

🟢

If Mitigated

No impact if the vulnerability is patched or the brd module is not loaded.

🌐 Internet-Facing: LOW - This requires local access or ability to load kernel modules, which typically requires elevated privileges.

🏢 Internal Only: MEDIUM - Malicious local users or compromised accounts with module loading privileges could exploit this to crash systems or potentially escalate privileges.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires ability to trigger module initialization failure scenarios, which may require specific conditions or fault injection techniques.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Fixed in stable kernel commits: 259bf925583ec9e3781df778cadf00594095090d, 410896624db639500f24f46478b4bfa05c76bf56, 41219c147df8bbd6591f59af5d695fb6c9a1cbff, 63dfd728b30f79495dacc886127695a379805152, 826cc42adf44930a633d11a5993676d85ddb0842

Vendor Advisory: https://git.kernel.org/stable/c/259bf925583ec9e3781df778cadf00594095090d

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. Reboot system to load patched kernel. 3. Verify brd module is not loaded or has been updated.

🔧 Temporary Workarounds

Disable brd module loading

linux

Prevent the vulnerable brd module from being loaded

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

Blacklist brd module

linux

Add brd to kernel module blacklist

echo 'blacklist brd' >> /etc/modprobe.d/blacklist-brd.conf

🧯 If You Can't Patch

Ensure brd module is not loaded (check with 'lsmod | grep brd')
Restrict module loading privileges to trusted users only

🔍 How to Verify

Check if Vulnerable:

Check if brd module is loaded: 'lsmod | grep -i brd'. If loaded, check kernel version against patched versions.

Check Version:

uname -r

Verify Fix Applied:

Check kernel version includes fix commits: 'uname -r' and verify against patched kernel versions. Also verify brd module is either not loaded or from patched kernel.

📡 Detection & Monitoring

Log Indicators:

Kernel oops messages mentioning brd_init, brd_alloc, or use-after-free
System crashes/panics during module loading
Failed modprobe brd commands in system logs

Network Indicators:

None - this is a local kernel vulnerability

SIEM Query:

source="kernel" AND ("brd_init" OR "brd_alloc" OR "UAF" OR "use-after-free")

📊 Metadata

CVE ID: CVE-2024-56693

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: December 28, 2024

Last Updated: November 3, 2025

🔗 References

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