CVE-2024-56581
📋 TL;DR
This CVE describes a use-after-free vulnerability in the Linux kernel's Btrfs filesystem ref-verify feature. When an invalid reference action occurs during Btrfs operations, the kernel fails to properly clean up memory references, potentially allowing attackers to crash the system or execute arbitrary code. Systems using Btrfs filesystems with ref-verify enabled are affected.
💻 Affected Systems
- Linux kernel
📦 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 →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 privilege escalation to kernel-level code execution allowing complete system compromise.
Likely Case
System instability, kernel crashes, or denial of service affecting Btrfs operations and potentially causing data corruption.
If Mitigated
Minor performance impact or failed Btrfs operations without system compromise if proper memory protections are in place.
🎯 Exploit Status
Exploitation requires triggering specific Btrfs operations that cause invalid ref actions. The Syzbot report shows the vulnerability can be triggered through filesystem operations.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits: 4275ac2741941c9c7c2293619fdbacb9f70ba85b, 6370db28af9a8ae3bbdfe97f8a48f8f995e144cf, 6fd018aa168e472ce35be32296d109db6adb87ea, 7c4e39f9d2af4abaf82ca0e315d1fd340456620f, a6f9e7a0bf1185c9070c0de03bb85eafb9abd650
Vendor Advisory: https://git.kernel.org/stable/c/4275ac2741941c9c7c2293619fdbacb9f70ba85b
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version. 2. Check distribution-specific security advisories. 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable Btrfs ref-verify
linuxDisable the Btrfs ref-verify feature if not required
echo 0 > /sys/module/btrfs/parameters/ref_verify
Avoid Btrfs filesystem
linuxUse alternative filesystems if Btrfs is not required
🧯 If You Can't Patch
- Restrict local user access to systems using Btrfs
- Implement strict process isolation and limit Btrfs operations
🔍 How to Verify
Check if Vulnerable:
Check kernel version and verify if Btrfs ref-verify is enabled: cat /sys/module/btrfs/parameters/ref_verifyCheck Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits and test Btrfs operations that previously triggered errors📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages
- Btrfs error logs mentioning 'Ref action'
- Use-after-free kernel warnings
SIEM Query:
source="kernel" AND ("BTRFS error" OR "use-after-free" OR "ref action")🔗 References
- https://git.kernel.org/stable/c/4275ac2741941c9c7c2293619fdbacb9f70ba85b
- https://git.kernel.org/stable/c/6370db28af9a8ae3bbdfe97f8a48f8f995e144cf
- https://git.kernel.org/stable/c/6fd018aa168e472ce35be32296d109db6adb87ea
- https://git.kernel.org/stable/c/7c4e39f9d2af4abaf82ca0e315d1fd340456620f
- https://git.kernel.org/stable/c/a6f9e7a0bf1185c9070c0de03bb85eafb9abd650
- https://git.kernel.org/stable/c/d2b85ce0561fde894e28fa01bd5d32820d585006
- https://git.kernel.org/stable/c/dfb9fe7de61f34cc241ab3900bdde93341096e0e
- https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html
- https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html
