CVE-2025-38220
📋 TL;DR
A NULL pointer dereference vulnerability in the Linux kernel's ext4 filesystem can cause kernel crashes when processing orphaned symlink inodes. This affects Linux systems using ext4 with data journaling enabled. The vulnerability is triggered during orphan cleanup operations.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to system crash and denial of service, potentially causing data corruption or loss if the crash occurs during critical filesystem operations.
Likely Case
System crash or kernel panic when orphaned symlink inodes are processed during filesystem operations, resulting in temporary denial of service.
If Mitigated
No impact if the system is patched or doesn't use ext4 with data journaling for symlinks.
🎯 Exploit Status
Exploitation requires specific conditions: ext4 with data journaling, orphaned symlink inodes, and triggering orphan cleanup. Likely discovered through fstest generic/388 testing.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits: be5f3061a6f904e3674257879e71881ceee5b673, cf6a4c4ac7b6e3214f25df594c9689a62f1bb456, d7af6eee8cd60f55aa8c5fe2b91f11ec0c9a0f27, e26268ff1dcae5662c1b96c35f18cfa6ab73d9de
Vendor Advisory: https://git.kernel.org/stable/c/be5f3061a6f904e3674257879e71881ceee5b673
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution. 2. Reboot system to load new kernel. 3. Verify kernel version after reboot.
🔧 Temporary Workarounds
Disable data journaling for ext4
linuxMount ext4 filesystems without data journaling (use journal=ordered or journal=writeback)
mount -o remount,journal=ordered /mount/point
Add 'journal=ordered' to /etc/fstab for ext4 partitions
Avoid orphaned symlinks
linuxEnsure proper filesystem cleanup and avoid abrupt system shutdowns that could leave orphaned inodes
🧯 If You Can't Patch
- Monitor system logs for kernel panic/crash events related to ext4
- Implement strict access controls to prevent local users from creating/manipulating symlinks in sensitive areas
🔍 How to Verify
Check if Vulnerable:
Check if running kernel version contains vulnerable ext4 code. Run: uname -r and compare with affected versions. Check if ext4 filesystems use data journaling: mount | grep ext4Check Version:
uname -rVerify Fix Applied:
Verify kernel version after update matches patched version. Check that ext4_dirty_journalled_data() helper properly handles symlink inodes.📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages mentioning ext4_block_zero_page_range
- NULL pointer dereference errors in kernel logs
- Filesystem corruption errors
Network Indicators:
- None - this is a local filesystem vulnerability
SIEM Query:
source="kernel" AND ("ext4_block_zero_page_range" OR "NULL pointer dereference" AND "ext4")