CVE-2025-21751
📋 TL;DR
A use-after-free vulnerability in the Linux kernel's mlx5 driver when handling firmware errors during matcher disconnect operations. This vulnerability could allow local attackers to crash the system or potentially execute arbitrary code. Affects systems using Mellanox/NVIDIA ConnectX network adapters with vulnerable kernel versions.
💻 Affected Systems
- Linux kernel with mlx5 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 →⚠️ Risk & Real-World Impact
Worst Case
Local privilege escalation leading to kernel compromise and full system control
Likely Case
Kernel panic or system crash causing denial of service
If Mitigated
Limited to denial of service with proper isolation and privilege restrictions
🎯 Exploit Status
Requires local access and ability to trigger specific firmware error conditions
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits 1ce840c7a659aa53a31ef49f0271b4fd0dc10296, 23a86c76a1a197e8fbbbd0ce3e826eb58c471624, or 5682aad0276ff9b9b0eff3188eb6a1f504d6b436
Vendor Advisory: https://git.kernel.org/stable/c/1ce840c7a659aa53a31ef49f0271b4fd0dc10296
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version 2. Reboot system 3. Verify kernel version and patch inclusion
🔧 Temporary Workarounds
Disable mlx5 driver
allPrevent loading of vulnerable mlx5 driver module
echo 'blacklist mlx5_core' >> /etc/modprobe.d/blacklist.conf
rmmod mlx5_core
🧯 If You Can't Patch
- Restrict local user access to systems with vulnerable configurations
- Implement strict privilege separation and limit users who can trigger network operations
🔍 How to Verify
Check if Vulnerable:
Check kernel version and verify if mlx5 driver is loaded: lsmod | grep mlx5Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes patch commits and mlx5 driver loads without errors📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages
- mlx5_core driver errors in dmesg
- Use-after-free kernel warnings
Network Indicators:
- Sudden loss of network connectivity on mlx5 interfaces
SIEM Query:
search 'kernel panic' OR 'mlx5_core' OR 'use-after-free' in system logs