CVE-2025-21940
📋 TL;DR
A NULL pointer dereference vulnerability exists in the Linux kernel's AMD KFD (Kernel Fusion Driver) component. This vulnerability allows local attackers to cause a kernel panic (denial of service) by triggering a specific IOCTL call sequence. Systems using AMD GPUs with the amdgpu driver are affected.
💻 Affected Systems
- Linux kernel with AMD KFD/amdgpu driver
📦 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 and denial of service, potentially causing data loss or service disruption.
Likely Case
Local denial of service through kernel panic, requiring system reboot to restore functionality.
If Mitigated
Minimal impact with proper access controls preventing local users from accessing KFD IOCTL interfaces.
🎯 Exploit Status
Discovered through fuzzing; requires local access and ability to call KFD IOCTLs.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel stable versions containing commit 049e5bf3c8406f87c3d8e1958e0a16804fa1d530
Vendor Advisory: https://git.kernel.org/stable/c/33eb8041c5d6c19d46e7bfd23a031844336afd80
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from official distribution repositories. 2. Reboot system to load new kernel. 3. Verify kernel version matches patched release.
🔧 Temporary Workarounds
Disable KFD module
linuxPrevent loading of the vulnerable KFD kernel module
echo 'blacklist amdkfd' >> /etc/modprobe.d/blacklist.conf
rmmod amdkfd
Restrict KFD device access
linuxLimit access to KFD device files to prevent exploitation
chmod 600 /dev/kfd
chown root:root /dev/kfd
🧯 If You Can't Patch
- Restrict local user access to systems with AMD GPUs
- Implement strict access controls on /dev/kfd device file
🔍 How to Verify
Check if Vulnerable:
Check if KFD module is loaded: lsmod | grep amdkfd. If loaded and kernel version is unpatched, system is vulnerable.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes fix commit: grep -q '049e5bf3c8406f87c3d8e1958e0a16804fa1d530' /proc/version_signature📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages in /var/log/kern.log or dmesg
- NULL pointer dereference errors mentioning kfd_queue_acquire_buffers
Network Indicators:
- None - local exploitation only
SIEM Query:
source="kernel" AND ("NULL pointer dereference" OR "kernel panic") AND "kfd"