CVE-2025-21754
📋 TL;DR
A Linux kernel Btrfs filesystem vulnerability causes an assertion failure when splitting ordered extents after a transaction abort during direct I/O writes. This can lead to kernel panic and system crashes, affecting systems using Btrfs filesystems with direct I/O operations enabled.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to system crash and denial of service, potentially causing data corruption or loss in Btrfs filesystems.
Likely Case
System crash or kernel panic when transaction aborts occur during direct I/O operations on Btrfs filesystems.
If Mitigated
System remains stable with proper error handling; failed I/O operations return appropriate error codes instead of crashing.
🎯 Exploit Status
Exploitation requires triggering transaction abort during specific Btrfs direct I/O operations; primarily a reliability issue rather than security vulnerability.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check kernel commits: 0d85f5c2dd91df6b5da454406756f463ba923b69, 0ff88c2a742a7cbaa4d08507d864737d099b435a, 8ea8db4216d1029527ab4666f730650419451e32, 927b930f117bbae730a853c1dc43da8afe8380fa
Vendor Advisory: https://git.kernel.org/stable/c/0d85f5c2dd91df6b5da454406756f463ba923b69
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix commits. 2. Reboot system to load new kernel. 3. Verify kernel version matches patched release.
🔧 Temporary Workarounds
Disable direct I/O on Btrfs
linuxPrevent use of direct I/O operations on Btrfs filesystems to avoid triggering the vulnerability
mount -o remount,nodiratime,noatime /path/to/btrfs
Use alternative filesystem
linuxTemporarily use ext4 or other filesystems for critical operations
🧯 If You Can't Patch
- Monitor system logs for Btrfs transaction abort errors and kernel panic events
- Implement high availability/failover for critical systems using Btrfs
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if using Btrfs filesystem with direct I/O operationsCheck Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits and test direct I/O operations on Btrfs📡 Detection & Monitoring
Log Indicators:
- BTRFS error: Transaction aborted
- kernel panic
- assertion failure in btrfs_split_ordered_extent
SIEM Query:
source="kernel" AND ("BTRFS error" OR "Transaction aborted" OR "assertion failure")