CVE-2025-21811
📋 TL;DR
A race condition vulnerability in the Linux kernel's nilfs2 filesystem could lead to use-after-free issues when buffers lose protection during asynchronous clearing. This affects systems using the nilfs2 filesystem and could result in system crashes or potential privilege escalation. The vulnerability requires local access to exploit.
💻 Affected Systems
- Linux kernel with nilfs2 filesystem support
📦 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 →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 or potential privilege escalation to kernel-level access, enabling full system compromise.
Likely Case
System instability, kernel crashes, or denial of service affecting nilfs2 filesystem operations.
If Mitigated
Minimal impact with proper access controls and monitoring; isolated crashes in nilfs2 operations.
🎯 Exploit Status
Requires local access and knowledge of nilfs2 filesystem operations to trigger the race condition.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits: 367a9bffabe08c04f6d725032cce3d891b2b9e1a, 4b08d23d7d1917bef4fbee8ad81372f49b006656, 58c27fa7a610b6e8d44e6220e7dbddfbaccaf439, 72cf688d0ce7e642b12ddc9b2a42524737ec1b4a, 8e1b9201c9a24638cf09c6e1c9f224157328010b
Vendor Advisory: https://git.kernel.org/stable/c/367a9bffabe08c04f6d725032cce3d891b2b9e1a
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version. 2. Check distribution-specific security advisories. 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable nilfs2 module
LinuxPrevent loading of nilfs2 kernel module to eliminate attack surface
echo 'install nilfs2 /bin/true' >> /etc/modprobe.d/disable-nilfs2.conf
rmmod nilfs2 2>/dev/null || true
🧯 If You Can't Patch
- Restrict user access to systems using nilfs2 filesystems
- Implement monitoring for kernel panic/crash events related to filesystem operations
🔍 How to Verify
Check if Vulnerable:
Check if nilfs2 module is loaded: lsmod | grep nilfs2. Check kernel version against patched commits.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits. Ensure nilfs2 operations complete without crashes.📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages
- Filesystem corruption errors in dmesg
- nilfs2-related error messages
Network Indicators:
- None - local vulnerability only
SIEM Query:
source="kernel" AND ("panic" OR "nilfs2" OR "use-after-free")🔗 References
- https://git.kernel.org/stable/c/367a9bffabe08c04f6d725032cce3d891b2b9e1a
- https://git.kernel.org/stable/c/4b08d23d7d1917bef4fbee8ad81372f49b006656
- https://git.kernel.org/stable/c/58c27fa7a610b6e8d44e6220e7dbddfbaccaf439
- https://git.kernel.org/stable/c/72cf688d0ce7e642b12ddc9b2a42524737ec1b4a
- https://git.kernel.org/stable/c/8e1b9201c9a24638cf09c6e1c9f224157328010b
- https://git.kernel.org/stable/c/c437dfac9f7a5a46ac2a5e6d6acd3059e9f68188
- https://git.kernel.org/stable/c/d8ff250e085a4c4cdda4ad1cdd234ed110393143
- https://git.kernel.org/stable/c/e1fc4a90a90ea8514246c45435662531975937d9
- https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
- https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
