CVE-2023-52681
📋 TL;DR
This CVE describes a memory leak vulnerability in the Linux kernel's efivarfs filesystem where the s_fs_info structure isn't properly freed during unmount. This affects Linux systems using efivarfs for EFI variable storage, potentially leading to memory exhaustion over time. 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 →⚠️ Risk & Real-World Impact
Worst Case
An attacker with local access could repeatedly mount/unmount efivarfs to cause kernel memory exhaustion, leading to system instability, denial of service, or potential kernel crashes.
Likely Case
Memory leak gradually consumes kernel memory over time, potentially causing performance degradation or system instability after many mount/unmount cycles.
If Mitigated
With proper access controls limiting who can mount filesystems, the impact is minimal as the vulnerability requires local access to trigger.
🎯 Exploit Status
Exploitation requires local access and ability to mount/unmount efivarfs filesystem.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Multiple stable kernel versions with fixes available (see git.kernel.org references)
Vendor Advisory: https://git.kernel.org/stable/c/547713d502f7b4b8efccd409cff84d731a23853b
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution's repositories. 2. Reboot system to load new kernel. 3. Verify kernel version matches patched release.
🔧 Temporary Workarounds
Restrict efivarfs mounting
linuxLimit which users can mount efivarfs filesystem to reduce attack surface
# Add to /etc/fstab: none /sys/firmware/efi/efivars efivarfs defaults,noauto 0 0
# Then manually mount only when needed
🧯 If You Can't Patch
- Implement strict access controls to prevent unauthorized users from mounting/unmounting filesystems
- Monitor system memory usage and kernel logs for signs of memory exhaustion
🔍 How to Verify
Check if Vulnerable:
Check kernel version and compare against patched releases from kernel.org or your distribution's security advisoriesCheck Version:
uname -rVerify Fix Applied:
Verify kernel version after update and check that efivarfs mounts/unmounts without memory leaks using system monitoring tools📡 Detection & Monitoring
Log Indicators:
- Kernel oom-killer messages
- System memory exhaustion warnings
- Repeated efivarfs mount/unmount operations in system logs
Network Indicators:
- None - local vulnerability only
SIEM Query:
source="kernel" AND ("out of memory" OR "oom-killer" OR "efivarfs")🔗 References
- https://git.kernel.org/stable/c/547713d502f7b4b8efccd409cff84d731a23853b
- https://git.kernel.org/stable/c/92be3095c6ca1cdc46237839c6087555be9160e3
- https://git.kernel.org/stable/c/48be1364dd387e375e1274b76af986cb8747be2c
- https://git.kernel.org/stable/c/547713d502f7b4b8efccd409cff84d731a23853b
- https://git.kernel.org/stable/c/92be3095c6ca1cdc46237839c6087555be9160e3
- https://git.kernel.org/stable/c/ea6b597fcaca99562fa56a473bcbbbd79b40af03
