CVE-2023-3111
📋 TL;DR
A use-after-free vulnerability in the Linux kernel's Btrfs filesystem allows local attackers to potentially crash the system or execute arbitrary code with kernel privileges. This affects Linux systems using Btrfs filesystems where users have access to the relevant ioctl commands. The vulnerability requires local access to trigger.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Local privilege escalation to kernel-level code execution, leading to complete system compromise, data corruption, or persistent backdoor installation.
Likely Case
Kernel panic or system crash causing denial of service, potentially leading to data loss on Btrfs volumes.
If Mitigated
Limited to denial of service if exploit fails or system has additional hardening, but still risks system instability.
🎯 Exploit Status
Exploitation requires calling specific ioctl sequences (btrfs_ioctl_balance before btrfs_ioctl_defrag) with appropriate permissions. No public exploit code has been released as of analysis.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in Linux kernel versions 5.15.90, 5.19.17, 6.0.15, 6.1.1 and later
Vendor Advisory: https://www.debian.org/security/2023/dsa-5480
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version via distribution package manager. 2. For Debian/Ubuntu: apt update && apt upgrade linux-image-*. 3. For RHEL/CentOS: yum update kernel. 4. Reboot system to load new kernel.
🔧 Temporary Workarounds
Restrict ioctl access
linuxLimit access to Btrfs ioctl commands using SELinux/AppArmor or capability restrictions
# Example AppArmor rule: deny /dev/btrfs-control rw,
# Remove CAP_SYS_ADMIN from non-privileged users
Disable Btrfs or use alternative filesystem
linuxAvoid using Btrfs filesystem if not required
# Check Btrfs usage: findmnt -t btrfs
# Consider migrating to ext4 or xfs if possible
🧯 If You Can't Patch
- Implement strict access controls to prevent non-privileged users from executing Btrfs ioctl commands
- Monitor for suspicious Btrfs-related system calls and kernel panic events
🔍 How to Verify
Check if Vulnerable:
Check kernel version: uname -r and compare against affected versions. Also verify Btrfs usage: lsmod | grep btrfs and findmnt -t btrfsCheck Version:
uname -rVerify Fix Applied:
Confirm kernel version is 5.15.90+, 5.19.17+, 6.0.15+, or 6.1.1+ with uname -r. Test that Btrfs operations work normally.📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages in /var/log/kern.log or dmesg
- Multiple btrfs_ioctl_balance and btrfs_ioctl_defrag calls from same process
- Use-after-free or NULL pointer dereference kernel oops
Network Indicators:
- Not applicable - local vulnerability
SIEM Query:
source="kernel" AND ("panic" OR "oops" OR "use-after-free") AND "btrfs"🔗 References
- https://lists.debian.org/debian-lts-announce/2023/07/msg00030.html
- https://lists.debian.org/debian-lts-announce/2023/10/msg00027.html
- https://patchwork.kernel.org/project/linux-btrfs/patch/20220721074829.2905233-1-r33s3n6%40gmail.com/
- https://security.netapp.com/advisory/ntap-20230703-0007/
- https://www.debian.org/security/2023/dsa-5480
- https://lists.debian.org/debian-lts-announce/2023/07/msg00030.html
- https://lists.debian.org/debian-lts-announce/2023/10/msg00027.html
- https://patchwork.kernel.org/project/linux-btrfs/patch/20220721074829.2905233-1-r33s3n6%40gmail.com/
- https://security.netapp.com/advisory/ntap-20230703-0007/
- https://www.debian.org/security/2023/dsa-5480
