CVE-2025-21988
📋 TL;DR
A race condition in the Linux kernel's netfs read collection subsystem can cause data corruption and kernel crashes when multiple subrequests donate data to the same request. This affects all Linux systems using the netfs subsystem, particularly those with network filesystems or caching layers.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to system crash and denial of service, potentially causing data loss or corruption in files being read.
Likely Case
System instability or crashes when accessing files through affected network filesystem paths, resulting in denial of service.
If Mitigated
Minor performance impact from the patch; systems remain stable with proper patching.
🎯 Exploit Status
Requires triggering specific race condition in filesystem operations; not trivial to exploit but could be discovered through fuzzing.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Patches available in stable kernel branches (commits: 62b9ad7e52d4777f7e775ee1f0ad2452f6041024, e25cec3b76aba47a49138d2162fc809c6cd49c9e, e2d46f2ec332533816417b60933954173f602121)
Vendor Advisory: https://git.kernel.org/stable/c/62b9ad7e52d4777f7e775ee1f0ad2452f6041024
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix. 2. For distributions: Use package manager (apt/yum/dnf) to update kernel package. 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable netfs subsystem
linuxAvoid using network filesystems or caching layers that rely on netfs subsystem
🧯 If You Can't Patch
- Monitor systems for kernel crashes or instability related to filesystem operations
- Limit use of network filesystems and implement redundancy for critical services
🔍 How to Verify
Check if Vulnerable:
Check kernel version and whether netfs subsystem is in use. Vulnerable if using affected kernel version with netfs.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits or is newer than patched versions.📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages mentioning 'Can't donate prior to front'
- System crashes during filesystem operations
- dmesg errors related to netfs or BUG()
SIEM Query:
Search for kernel panic events or BUG() messages in system logs